LibC: Implement getwchar()

Userland/Libraries/LibC/wchar.h

@@ -73,5 +73,6 @@ size_t wcsspn(const wchar_t* wcs, const wchar_t* accept);
 
 wint_t fgetwc(FILE* stream);
 wint_t getwc(FILE* stream);
+wint_t getwchar(void);
 
 __END_DECLS

Userland/Libraries/LibC/wstdio.cpp

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