tool_doswin: Improve sanitization processing

- Add unit test 1604 to test the sanitize_file_name function.

- Use -DCURL_STATICLIB when building libcurltool for unit testing.

- Better detection of reserved DOS device names.

- New flags to modify sanitize behavior:

SANITIZE_ALLOW_COLONS: Allow colons
SANITIZE_ALLOW_PATH: Allow path separators and colons
SANITIZE_ALLOW_RESERVED: Allow reserved device names
SANITIZE_ALLOW_TRUNCATE: Allow truncating a long filename

- Restore sanitization of banned characters from user-specified outfile.

Prior to this commit sanitization of a user-specified outfile was
temporarily disabled in 2b6dadc because there was no way to allow path
separators and colons through while replacing other banned characters.
Now in such a case we call the sanitize function with
SANITIZE_ALLOW_PATH which allows path separators and colons to pass
through.


Closes https://github.com/curl/curl/issues/624
Reported-by: Octavio Schroeder

src/tool_doswin.h

@@ -25,7 +25,29 @@
 
 #if defined(MSDOS) || defined(WIN32)
 
-CURLcode sanitize_file_name(char **filename);
+#define SANITIZE_ALLOW_COLONS    (1<<0)  /* Allow colons */
+#define SANITIZE_ALLOW_PATH      (1<<1)  /* Allow path separators and colons */
+#define SANITIZE_ALLOW_RESERVED  (1<<2)  /* Allow reserved device names */
+#define SANITIZE_ALLOW_TRUNCATE  (1<<3)  /* Allow truncating a long filename */
+
+typedef enum {
+  SANITIZE_ERR_OK = 0,           /* 0 - OK */
+  SANITIZE_ERR_INVALID_PATH,     /* 1 - the path is invalid */
+  SANITIZE_ERR_BAD_ARGUMENT,     /* 2 - bad function parameter */
+  SANITIZE_ERR_OUT_OF_MEMORY,    /* 3 - out of memory */
+  SANITIZE_ERR_LAST /* never use! */
+} SANITIZEcode;
+
+SANITIZEcode sanitize_file_name(char **const sanitized, const char *file_name,
+                                int flags);
+#ifdef UNITTESTS
+SANITIZEcode truncate_dryrun(const char *path, const size_t truncate_pos);
+SANITIZEcode msdosify(char **const sanitized, const char *file_name,
+                      int flags);
+SANITIZEcode rename_if_reserved_dos_device_name(char **const sanitized,
+                                                const char *file_name,
+                                                int flags);
+#endif /* UNITTESTS */
 
 #if defined(MSDOS) && (defined(__DJGPP__) || defined(__GO32__))