hooks.c: New file.

* hooks.c: New file.
* hooks.h: New file.
* Makefile.in (HOOKS_H): New.
(TARGET_DEF_H): Added $(HOOKS_H).
(OBJS): Added hooks.o.
(cfgcleanup.o, bb-reorder.o): Added target.h.
(hooks.o): Added dependencies.
* target-def.h (TARGET_CANNOT_MODIFY_JUMPS_P): New, added to...
(TARGET_INITIALIZER): this.
* doc/tm.texi (TARGET_CANNOT_MODIFY_JUMPS_P): Document.
* target.h (struct gcc_target): Added cannot_modify_jumps_p.
* bb-reorder.c: Include target.h.
(reorder_basic_blocks): Skip if cannot modify jumps.
* cfgcleanup.c: Include target.h.
(try_optimize_cfg): Skip merge blocking if cannot modify jumps.

From-SVN: r49627