Remove configure --disable-float4-byval and --disable-float8-byval

AFAICT, these build options were only useful to maintain compatibility
for version-0 functions, but those are no longer supported, so these
options can be removed. There is a fair amount of code all over the
place to support these options, so the cleanup is quite significant.

The current behavior became the default in PG9.3. Note that this does
not affect on-disk storage. The only upgrade issue that I can see is
that pg_upgrade refuses to upgrade incompatible clusters if you have
contrib/isn installed. But hopefully everyone who is affected by that
will have upgraded at least once since PG9.2 already.

float4 is now always pass-by-value; the pass-by-reference code path is
completely removed.

float8 and related types are now hardcoded to pass-by-value or
pass-by-reference depending on whether the build is 64- or 32-bit, as
was previously also the default.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services