patch 8.0.0175: setting language on MS-Windows does not always work

Problem:    Setting language in gvim on MS-Windows does not work when
            libintl.dll is dynamically linked with msvcrt.dll.
Solution:   Use putenv() from libintl as well. (Ken Takata, closes #1082)
diff --git a/src/proto/os_win32.pro b/src/proto/os_win32.pro
index b21a7ba..a64c863 100644
--- a/src/proto/os_win32.pro
+++ b/src/proto/os_win32.pro
@@ -1,5 +1,7 @@
 /* os_win32.c */
 HINSTANCE vimLoadLib(char *name);
+HINSTANCE find_imported_module_by_funcname(HINSTANCE hInst, const char *funcname);
+void *get_dll_import_func(HINSTANCE hInst, const char *funcname);
 int dyn_libintl_init(void);
 void dyn_libintl_end(void);
 void PlatformId(void);