Add test to make sure GDB knows which "kind" of watchpoint the target has

Add test to make sure GDB knows which "kind" of watchpoint the target has

This adds a test that makes sure GDB knows whether the target has
continuable, or non-continuable watchpoints.

That is, the test confirms that GDB presents a watchpoint value change
at the first instruction right after the instruction that changes
memory.

gdb/testsuite/ChangeLog:
2014-09-16  Pedro Alves  <palves@redhat.com>

	* gdb.base/watchpoint-stops-at-right-insn.c: New file.
	* gdb.base/watchpoint-stops-at-right-insn.exp: New file.