LibC: Add stub for iswprint

Without the declaration of iswprint libarchive will not compile.

Userland/Libraries/LibC/wctype.cpp

@@ -21,4 +21,10 @@ int iswctype(wint_t, wctype_t)
     dbgln("FIXME: Implement iswctype()");
     TODO();
 }
+
+int iswprint(wint_t)
+{
+    dbgln("FIXME: Implement iswprint()");
+    TODO();
+}
 }

Userland/Libraries/LibC/wctype.h

@@ -12,5 +12,6 @@ __BEGIN_DECLS
 
 wctype_t wctype(const char* name);
 int iswctype(wint_t wc, wctype_t desc);
+int iswprint(wint_t wc);
 
 __END_DECLS