pgsql: Properly support multi-line entires (such as OBJS=) when building

Log Message:
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Properly support multi-line entires (such as OBJS=) when building
PROGRAM, not just MODULE, in contrib.

Modified Files:
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pgsql/src/tools/msvc:
Mkvcbuild.pm (r1.55 -> r1.56)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/tools/msvc/Mkvcbuild.pm?r1=1.55&r2=1.56)