S390: Hardware breakpoint support

S390: Hardware breakpoint support

Add hardware breakpoint support for S390 targets.

gdb/ChangeLog:

	* s390-linux-nat.c (PER_BIT, PER_EVENT_BRANCH, PER_EVENT_IFETCH)
	(PER_EVENT_STORE, PER_EVENT_NULLIFICATION)
	(PER_CONTROL_BRANCH_ADDRESS, PER_CONTROL_SUSPENSION)
	(PER_CONTROL_ALTERATION): New macros.
	(struct s390_debug_reg_state) <break_areas>: New member.
	(s390_forget_process): Free break_areas as well.
	(s390_linux_new_fork): Copy break_areas as well.
	(s390_prepare_to_resume): Install hardware breakpoints.
	(s390_can_use_hw_breakpoint): Indicate support for hardware
	breakpoints.
	(s390_insert_hw_breakpoint, s390_remove_hw_breakpoint): New
	linux_nat target methods.
	(_initialize_s390_nat): Register them.

gdb/testsuite/ChangeLog:

	* lib/gdb.exp: No longer skip hardware breakpoint tests on s390.