LibC: Use __inline_isascii() in isascii()

Userland/Libraries/LibC/ctype.cpp

@@ -116,7 +116,7 @@ int islower(int c)
 #undef isascii
 int isascii(int c)
 {
-    return ((unsigned)c <= 127);
+    return __inline_isascii(c);
 }
 
 #undef isblank