core: make libintl.h required if CMake option ENABLE_NLS is enabled (issue #2031)

src/core/wee-doc.c

@@ -1658,9 +1658,11 @@ doc_generate (const char *path)
      * (this is used to generate documentation without installing WeeChat,
      * that means no need to run `make install`)
      */
+#ifdef ENABLE_NLS
     localedir = getenv ("WEECHAT_DOCGEN_LOCALEDIR");
     if (localedir && localedir[0])
         bindtextdomain (PACKAGE, localedir);
+#endif /* ENABLE_NLS */
 
     for (i = 0; locales[i]; i++)
     {

src/core/weechat.h

@@ -33,11 +33,7 @@
 #include <locale.h>
 
 #if defined(ENABLE_NLS) && !defined(_)
-    #ifdef HAVE_LIBINTL_H
-        #include <libintl.h>
-    #else
-        #include "../../intl/libintl.h"
-    #endif /* HAVE_LIBINTL_H */
+    #include <libintl.h>
     #define _(string) gettext(string)
     #define NG_(single,plural,number) ngettext(single,plural,number)
     #ifdef gettext_noop