Log Message:
Use the extended PLIST_SRC support which now also reads:
PLIST.${MACHINE_ARCH:C/i[3-6]86/i386/g}
PLIST.${OPSYS}-${MACHINE_ARCH:C/i[3-6]86/i386/g}
and remove the package hack for MD PLIST files.

PLIST.* files renamed so we don't need the special handling for MACHINE32_ARCH.
Merge the PLIST.* files as much as possible into PLIST, so they only
contain the difference between the two archs which are only supported by
this package.