add cescape stuff and two tests

test/textcode.c

@@ -0,0 +1,21 @@
+#include "array.h"
+#include "textcode.h"
+#include <assert.h>
+
+array a;
+
+int main() {
+  char buf[256];
+  int i;
+  for (i=0; i<256; ++i) buf[i]=i;
+
+  fmt_to_array(fmt_uuencoded,&a,buf,256);
+  assert(!array_failed(&a));
+  write(1,array_start(&a),array_bytes(&a));
+  array_trunc(&a);
+
+  fmt_to_array(fmt_base64,&a,buf,256);
+  assert(!array_failed(&a));
+  write(1,array_start(&a),array_bytes(&a)); write(1,"\n",1);
+  array_trunc(&a);
+}