Add in D'Arcy's cash code

pg_proc.h still needs modifying, but this gets it in there so that we can
get around any compiler bugs.  Will try and get the pg_proc.h entries done
up later tonight...

src/include/utils/cash.h

@@ -0,0 +1,16 @@
+/*
+cash.h
+Written by D'Arcy J.M. Cain
+
+functions to allow input and output of money normally but store
+and handle it as long integers
+*/
+
+#ifndef		_CASH_H
+#define		_CASH_H
+
+const char	*cash_out(long value);
+long		cash_in(const char *str);
+const char	*cash_words_out(long value);
+
+#endif		/* _CASH_H */