Log message:
Fix PLIST, slightly improve post-install. Bump revision.

Log message:
Import libmpg123-1.5.1.  This package provides the mpg123 project's
core decoder library, which the new mpg123 package will depend on.
Other software packages are beginning to write plug-ins for this
library, and so installing it seperately is worthwhile.

NOTE: I have encountered segfaults when attempting to use the jack
module, which is threaded, with mpg123 unless I linked mpg123 with
libpthread.  This may or may not apply to the library, though my
intuition is that it does not, as obviously the executable is
what calls lt_dlopen().  Thus, for now the Makefile and b3.mk of the 
executable will pull in dlopen.buildlink3.mk, setting 
DLOPEN_REQUIRE_PTHREADS=yes as necessary (last time I checked on
NetBSD 4.99, it was).