[PATCH] Move 'long long' check to c.h

Greetings,

  While reviewing bfba40e2c7b3909d3de13bd1b83b7e85fa8dfec2 (mmm, we like
  git diff -p), I noted that c.h is already included by both extern.h
  and ecpg.header through postgres_fe.h.  Given this and that we're
  already doing alot of similar #define's there (unlike in those other
  files), I felt c.h was a more appropriate place.  Putting it in c.h
  also means we don't have to duplicate that code.

  Patch attached.

      Thanks,

        Stephen