perl: Add 5.8.8 and use DEFAULT_PREFERENCE to disable it until more

perl: Add 5.8.8 and use DEFAULT_PREFERENCE to disable it until more
testing is done.
Main differences from the 5.8.7 recipe are:
* Always use gcc to link. Same arch's require this, while others can
  happily use ld. Use gcc for everything.
* Fix threading issues by enabling threading in both perl-native and
  perl. In fact make the configurations almost identical.
* No per ARCH configuration, just 32/64/le/be configs. This should
  stop configurations differing between arch's which made fixing
  things 5.8.7 difficult. Also means new ARCH's should work without
  any changes.
* Fix up the way miniperl is handled so it shouldn't be the cause of
  problems for people anymore.
* Stop perl-modules depending on perl-dbg, perl-pod, perl-dev etc.
* In theory should work for MACHINE="native" now.
Only tested for an sh4/glibc target built on an x86_64 host so far. A
lot more testing and more cleanups are needed before this is ready to
be enabled by default. NOTE: You must build the matching version of
perl-native before attempting to build perl (that applies for any
version).