Add missing string.c file.

Author: dvanhorn

langs/outlaw/string.c

@@ -0,0 +1,20 @@
+#include "values.h"
+
+int string_append(const val_str_t* s1, const val_str_t* s2, val_str_t* dest)
+{
+  if (!s1 && !s2) { return 0; }
+  int i1 = (s1 ? s1->len : 0);
+  int i2 = (s2 ? s2->len : 0);
+  int len = i1+i2;
+  dest->len = len;
+  int i;
+  if (s1) {
+    for (i = 0; i < s1->len; i++)
+      dest->codepoints[i] = s1->codepoints[i];
+  }
+  if (s2) {
+    for (i = 0; i < s2->len; i++)
+      dest->codepoints[i1 + i] = s2->codepoints[i];
+  }
+  return 2+len+((len % 2) == 0 ? 0 : 1);
+}