Assumptions on the number of hw watchpoints for some testcases

[Luis Machado <luisgpm@linux.vnet.ibm.com>]

Hi,

Recently i've noticed that some of the newer watchpoint-related
(watchpoint.exp, watchthreads.exp and local-watch-wrong-thread.exp for
example) testcases were failing due to the testcases themselves not
respecting the fact that PPC server processors only have a single HW
watchpoint register. Some of the testcases check for "watch *0x0" as a
means to tell if the platform actually supports doing "watch *var" in
HW. That doesn't work correctly on PPC server processors since "watch
*0x0" will use a HW watchpoint and "watch *var" will fall back to two SW
watchpoints...

I may declare watchthreads.exp unsupported for PPC server as it has a
strong assumption that the target can do 2 HW watchpoints or i can write
a different testcase relying on a single HW watchpoint.

As for the others, i'll try to make the tests more flexible.

I don't think GDB has a handy maint command to tell the testcases how
many HW watches a target can use.

Regards,
Luis