LibC: Add strcoll() and strxfrm().

These are obviously not locale-aware implementations, but rather really just
strcmp() and strcpy() with different names. This makes vim build and run :^)

LibC/string.cpp

@@ -369,5 +369,20 @@ char *strtok(char* str, const char* delim)
     ASSERT_NOT_REACHED();
 }
 
+int strcoll(const char* s1, const char* s2)
+{
+    return strcmp(s1, s2);
+}
+
+size_t strxfrm(char* dest, const char* src, size_t n)
+{
+    size_t i;
+    for (i = 0; i < n && src[i] != '\0'; ++i)
+        dest[i] = src[i];
+    for ( ; i < n; ++i)
+        dest[i] = '\0';
+    return i;
+}
+
 }