Add win32 initialization support to curl_global_init() and

curl_global_cleanup().  Update corresponding man pages...

Improve the logic in curl_global_cleanup() and curl_global_init() so that
they are not called twice if the application libraries have been
initialized and make sure to reset the init flags in curl_global_cleanup().

docs/TODO

@@ -20,11 +20,6 @@ To do in a future release (random order):
  * Consider an interface to libcurl that allows applications to easier get to
    know what cookies that are sent back in the response headers.
 
- * The win32_init() and win32_cleanup() functions that are present in
-   src/main.c (and docs/examples/win32sockets.c) would probably be fine to
-   add to curl_global_init() and performed if the correct flag is set. Makes
-   it easier for windows people.
-
  * Make SSL session ids get used if multiple HTTPS documents from the same
    host is requested. http://curl.haxx.se/dev/SSL_session_id.txt
 

docs/curl_global_init.3

@@ -27,10 +27,13 @@ This function was added in libcurl 7.8.
 .SH FLAGS
 .TP 5
 .B CURL_GLOBAL_ALL
-Initialise everyting possible. This sets all known bits.
+Initialize everyting possible. This sets all known bits.
 .TP
 .B CURL_GLOBAL_SSL
-Initialise SSL
+Initialize SSL
+.TP
+.B CURL_GLOBAL_WIN32
+Initialize the Win32 socket libraries.
 .TP
 .B CURL_GLOBAL_NOTHING
 Initialise nothing extra. This sets no bit.