add THANKS file

THANKS

@@ -0,0 +1,12 @@
+We p≡p Engine authors wish to thank:
+
+* Tom St Denis and the other authors of the excellent LibTomCrypt, from which we
+  reused the RIPEMD-160 hash implementation (while we are aware that the library
+  is in the public domain and an acknowledgement is not required we still wish
+  to freely express our gratitude);
+
+* the authors of libetpan;
+
+* the authors of asn1c;
+
+* [likely other people we are forgetting].