Update source code to Byron's v6.30.0250 sources plus minor cleanup

Update source code to Byron's v6.30.0250 sources plus minor cleanup
 to get rid of unused variables.
Get clean compile on Linux (Thomas and Gerald).
Implement autoconf/configure for standalone builds and use the existing
 autoconf/configure system when in the Postgres source tree.
Code tests and functions with ApplixWare-4.4.1beta on a Linux box.
Changes should be backward compatible with WIN32 but still needs testing.