pgsql: Release builds generate different strangely formatted export

Log Message:
-----------
Release builds generate different strangely formatted export names
for local symbols, that shouldn't be exported. This patch excludes them,
cutting down about 10,000 exported symbols and decreasing the binary size
by 20%.

Modified Files:
--------------
pgsql/src/tools/msvc:
gendef.pl (r1.5 -> r1.6)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/msvc/gendef.pl.diff?r1=1.5&r2=1.6)