tidy-up: misc

- lib1531: fix to use `curl_off_t`.
- src/tool_doswin: merge `_WIN32` guards.
- src/tool_doswin: limit `S_ISCHR()` to MS-DOS.
- src: dedupe `CURL_O_BINARY` macro into `tool_setup.h`.
- CMake/CurlTests.c: cleanup/formatting `HAVE_FILE_OFFSET_BITS` test.
- examples/httpput-postfields: delete unused include.
- spelling: MultiSSL.
- whitespace.

Ref: #15652
Closes #15799

tests/libtest/lib1531.c

@@ -31,7 +31,7 @@
 #define TEST_HANG_TIMEOUT 60 * 1000
 
 static char const testData[] = ".abc\0xyz";
-static off_t const testDataSize = sizeof(testData) - 1;
+static curl_off_t const testDataSize = sizeof(testData) - 1;
 
 CURLcode test(char *URL)
 {
@@ -57,8 +57,7 @@ CURLcode test(char *URL)
 
   /* set the options (I left out a few, you'll get the point anyway) */
   curl_easy_setopt(easy, CURLOPT_URL, URL);
-  curl_easy_setopt(easy, CURLOPT_POSTFIELDSIZE_LARGE,
-                   (curl_off_t)testDataSize);
+  curl_easy_setopt(easy, CURLOPT_POSTFIELDSIZE_LARGE, testDataSize);
   curl_easy_setopt(easy, CURLOPT_POSTFIELDS, testData);
 
   /* we start some action by calling perform right away */

tests/libtest/test.h

@@ -45,7 +45,7 @@
 #include "curl_printf.h"
 
 #ifdef _WIN32
-#define sleep(sec) Sleep ((sec)*1000)
+#define sleep(sec) Sleep((sec)*1000)
 #endif
 
 #define test_setopt(A,B,C)                                      \