pgsql: Fix bcc32.mak to create and remove pg_config_os.h properly.

Log Message:
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Fix bcc32.mak to create and remove pg_config_os.h properly. Apparently
win32.mak got patched for this, but not bcc32.mak.

Modified Files:
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pgsql/src:
bcc32.mak (r1.3 -> r1.4)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bcc32.mak.diff?r1=1.3&r2=1.4)