MSVC: Don't link libpgcommon into pgcrypto.

Doing so was useful in 273c458a2b but
became obsolete when 818fd4a67d caused
postgres.exe to provide the relevant symbols.  No other loadable module
links to libpgcommon directly.

src/tools/msvc/Mkvcbuild.pm

@@ -451,7 +451,6 @@ sub mkvcbuild
 			'imath.c');
 	}
 	$pgcrypto->AddReference($postgres);
-	$pgcrypto->AddReference($libpgcommon);
 	$pgcrypto->AddLibrary('ws2_32.lib');
 	my $mf = Project::read_file('contrib/pgcrypto/Makefile');
 	GenerateContribSqlFiles('pgcrypto', $mf);