pgsql: Add #include <float.h> for platforms that still need it.

Log Message:
-----------
Add #include <float.h> for platforms that still need it.

Modified Files:
--------------
pgsql/src/backend/utils/adt:
float.c (r1.132 -> r1.133)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/float.c.diff?r1=1.132&amp;r2=1.133)