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