LibC: Implement getwchar()

Author: https://github.com/alimpfard
Commit: a4e8a09188
Pull-request: https://github.com/SerenityOS/serenity/pull/11324
Reviewed-by: https://github.com/BertalanD

Userland/Libraries/LibC/wstdio.cpp

@@ -56,4 +56,9 @@ wint_t getwc(FILE* stream)
 {
     return fgetwc(stream);
 }
+
+wint_t getwchar()
+{
+    return getwc(stdin);
+}
 }