tidy-up: OS names

Use these words and casing more consistently across text, comments and
one curl tool output:
AIX, ALPN, ANSI, BSD, Cygwin, Darwin, FreeBSD, GitHub, HP-UX, Linux,
macOS, MS-DOS, MSYS, MinGW, NTLM, POSIX, Solaris, UNIX, Unix, Unicode,
WINE, WebDAV, Win32, winbind, WinIDN, Windows, Windows CE, Winsock.

Mostly OS names and a few more.

Also a couple of other minor text fixups.

Closes #14360

tests/server/resolve.c

@@ -38,7 +38,7 @@
 #include <netinet/in.h>
 #endif
 #ifdef _XOPEN_SOURCE_EXTENDED
-/* This define is "almost" required to build on HPUX 11 */
+/* This define is "almost" required to build on HP-UX 11 */
 #include <arpa/inet.h>
 #endif
 #ifdef HAVE_NETDB_H

tests/server/rtspd.c

@@ -106,7 +106,7 @@ struct httprequest {
   bool auth;      /* Authorization header present in the incoming request */
   size_t cl;      /* Content-Length of the incoming request */
   bool digest;    /* Authorization digest header found */
-  bool ntlm;      /* Authorization ntlm header found */
+  bool ntlm;      /* Authorization NTLM header found */
   int pipe;       /* if non-zero, expect this many requests to do a "piped"
                      request/response */
   int skip;       /* if non-zero, the server is instructed to not read this

tests/server/sockfilt.c

@@ -422,11 +422,11 @@ static bool read_data_block(unsigned char *buffer, ssize_t maxlen,
 
 #if defined(USE_WINSOCK) && !defined(CURL_WINDOWS_APP)
 /*
- * WinSock select() does not support standard file descriptors,
+ * Winsock select() does not support standard file descriptors,
  * it can only check SOCKETs. The following function is an attempt
  * to re-create a select() function with support for other handle types.
  *
- * select() function with support for WINSOCK2 sockets and all
+ * select() function with support for Winsock2 sockets and all
  * other handle types supported by WaitForMultipleObjectsEx() as
  * well as disk files, anonymous and names pipes, and character input.
  *
@@ -683,7 +683,7 @@ static int select_ws(int nfds, fd_set *readfds, fd_set *writefds,
   /* loop over the handles in the input descriptor sets */
   nfd = 0; /* number of handled file descriptors */
   nth = 0; /* number of internal waiting threads */
-  nws = 0; /* number of handled WINSOCK sockets */
+  nws = 0; /* number of handled Winsock sockets */
   for(fd = 0; fd < nfds; fd++) {
     wsasock = curlx_sitosk(fd);
     wsaevents.lNetworkEvents = 0;
@@ -829,7 +829,7 @@ static int select_ws(int nfds, fd_set *readfds, fd_set *writefds,
         FD_CLR(wsasock, exceptfds);
       }
       else {
-        /* try to handle the event with the WINSOCK2 functions */
+        /* try to handle the event with the Winsock2 functions */
         wsaevents.lNetworkEvents = 0;
         error = WSAEnumNetworkEvents(wsasock, handle, &wsaevents);
         if(error != SOCKET_ERROR) {

tests/server/socksd.c

@@ -1117,7 +1117,7 @@ int main(int argc, char *argv[])
 
 #ifdef USE_UNIX_SOCKETS
   if(socket_domain == AF_UNIX)
-    logmsg("Listening on unix socket %s", unix_socket);
+    logmsg("Listening on Unix socket %s", unix_socket);
   else
 #endif
   logmsg("Listening on port %hu", port);

tests/server/sws.c

@@ -109,7 +109,7 @@ struct httprequest {
   bool auth;      /* Authorization header present in the incoming request */
   size_t cl;      /* Content-Length of the incoming request */
   bool digest;    /* Authorization digest header found */
-  bool ntlm;      /* Authorization ntlm header found */
+  bool ntlm;      /* Authorization NTLM header found */
   int delay;      /* if non-zero, delay this number of msec after connect */
   int writedelay; /* if non-zero, delay this number of milliseconds between
                      writes in the response */

tests/server/util.c

@@ -28,7 +28,7 @@
 #include <netinet/in.h>
 #endif
 #ifdef _XOPEN_SOURCE_EXTENDED
-/* This define is "almost" required to build on HPUX 11 */
+/* This define is "almost" required to build on HP-UX 11 */
 #include <arpa/inet.h>
 #endif
 #ifdef HAVE_NETDB_H
@@ -143,7 +143,7 @@ static const char *win32_strerror(int err, char *buf, size_t buflen)
   return buf;
 }
 
-/* use instead of perror() on generic windows */
+/* use instead of perror() on generic Windows */
 void win32_perror(const char *msg)
 {
   char buf[512];
@@ -166,7 +166,7 @@ void win32_init(void)
 
   if(err) {
     perror("Winsock init failed");
-    logmsg("Error initialising winsock -- aborting");
+    logmsg("Error initialising Winsock -- aborting");
     exit(1);
   }
 
@@ -190,7 +190,7 @@ void win32_cleanup(void)
   _flushall();
 }
 
-/* socket-safe strerror (works on WinSock errors, too */
+/* socket-safe strerror (works on Winsock errors, too */
 const char *sstrerror(int err)
 {
   static char buf[512];
@@ -550,7 +550,7 @@ static void exit_signal_handler(int signum)
  * They are included for ANSI compatibility. Therefore, you can set
  * signal handlers for these signals by using signal, and you can also
  * explicitly generate these signals by calling raise. Source:
- * https://docs.microsoft.com/de-de/cpp/c-runtime-library/reference/signal
+ * https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/signal
  */
 static BOOL WINAPI ctrl_event_handler(DWORD dwCtrlType)
 {
@@ -690,7 +690,7 @@ static SIGHANDLER_T set_signal(int signum, SIGHANDLER_T handler,
 void install_signal_handlers(bool keep_sigalrm)
 {
 #ifdef _WIN32
-  /* setup windows exit event before any signal can trigger */
+  /* setup Windows exit event before any signal can trigger */
   exit_event = CreateEvent(NULL, TRUE, FALSE, NULL);
   if(!exit_event)
     logmsg("cannot create exit event");