GLib: Add forgotten includes and build fixes

-gcharset.c, genviron.c, gunicollate.c: Some headers were missed in those
 files that triggered C4013 warnings/errors (aka. implicit declaration
 of ... in GCC).  Make up for them here.
-gwin32.h: Only define g_win32_get_package_installation_directory/
 g_win32_get_package_installation_subdirectory as macros
 (alias of g_win32_get_package_installation_directory_utf8/
 g_win32_get_package_installation_subdirectory_utf8) on Win64 (x64) as
 g_win32_get_package_installation_directory/
 g_win32_get_package_installation_subdirectory have seperate existing
 implmentations for Win32-this is a long-standing problem but was covered-
 up by G_DISABLE_DEPRECATED, which we are stopping to use as of 2.31.0.

glib/gcharset.c

@@ -28,6 +28,9 @@
 #include "gmessages.h"
 #include "gstrfuncs.h"
 #include "gthread.h"
+#ifdef G_OS_WIN32
+#include "gwin32.h"
+#endif
 
 #include "libcharset/libcharset.h"
 

glib/genviron.c

@@ -36,10 +36,16 @@
 #ifdef HAVE_CRT_EXTERNS_H
 #include <crt_externs.h> /* for _NSGetEnviron */
 #endif
+#ifdef G_OS_WIN32
+#include <windows.h>
+#endif
 
 #include "gmem.h"
 #include "gmessages.h"
 #include "gstrfuncs.h"
+#include "gunicode.h"
+#include "gconvert.h"
+#include "gquark.h"
 
 /* Environ array functions {{{1 */
 static gint

glib/gunicollate.c

@@ -36,6 +36,7 @@
 #include "gstring.h"
 #include "gstrfuncs.h"
 #include "gtestutils.h"
+#include "gcharset.h"
 #ifndef __STDC_ISO_10646__
 #include "gconvert.h"
 #endif

glib/gwin32.h

@@ -86,9 +86,11 @@ gchar*          g_win32_error_message (gint error);
 #ifndef G_DISABLE_DEPRECATED
 
 #ifndef __GTK_DOC_IGNORE__
+#ifdef _WIN64
 #define g_win32_get_package_installation_directory g_win32_get_package_installation_directory_utf8
 #define g_win32_get_package_installation_subdirectory g_win32_get_package_installation_subdirectory_utf8
 #endif
+#endif
 
 gchar*          g_win32_get_package_installation_directory (const gchar *package,
 							    const gchar *dll_name);