libpq naming on Win64

There is likely to be a long period where many Windows packages for
PostgreSQL are 32 bit only. Due to the way Windows searches for DLLs,
Windows installations of PostgreSQL tend to install libpq.dll into the
bin/ directory of the installation. This will cause obvious problems
with 32 bit packages like pgAdmin which are currently included in that
directory in most installers, to avoid the need to have multiple
copies of DLLs around.

After chatting with Magnus, we feel that a good solution would be to
rename libpq on Win64 to libpq64.dll to distinguish it from the 32 bit
equivalent.

It would also be a nice touch to have the 64 bit MSVC build system
create both the 64 and 32 bit libraries. That would make it much
easier for those of us that need to combine 32 and 64 bit packages
together, saving the pain of building 32 and 64 bit separately.

Thoughts?

--
Dave Page
EnterpriseDB UK: http://www.enterprisedb.com