Improved version handling introduced by Dave Page.

The driver version is 07.01.0002 now.
1) initialized pg_version by DSN's protocol info
   so that we could always use pg_version info
   once a connection is established (pg_version()
   didn't exist before 6.4). PROTOCOL_XX() macros
   are removed(except from connection.[ch]).
2) provided a few macros to encapsulate connection's
   version info and replaced existent comparison
   stuff by those macros.
3) change SQLTables() so that 7.1 servers could show
   views.


In addtion, the following patch from Dave Page is applied.

  This patch fixes a bug in SQLGetInfo for SQL_DBMS_VER which corrupted the
  driver version string. The driver version number has also been incremented
  to 07.01.0002.

  Regards, Dave. <<odbc.diff>>