Add support for the CLZ insn

Will be used if pattern-compare is enabled and the targeted
core is newer than v8.10.a.

Changelog

2013-02-11  Edgar E. Iglesias <edgar.iglesias@gmail.com>

  * config/microblaze/microblaze.c: microblaze_has_clz = 0
     Add version check for v8.10.a to enable microblaze_has_clz
  * config/microblaze/microblaze.h: Add TARGET_HAS_CLZ as
     combined version and TARGET_PATTERN_COMPARE check
  * config/microblaze/microblaze.md: New clzsi2 instruction