Rename test.

Rename test.

I realized that the name of this test only made sense when considering
the old (never committed) implementation of the fix that came along
with the test originally, that forced a schedlock while a step-resume
(to get over the signal handler) was inserted.  The final solution
that went into the tree does not force that locking.

So this renames it to something more descriptive.

gdb/testsuite/
2014-02-21  Pedro Alves  <palves@redhat.com>

	* gdb.threads/step-after-sr-lock.c: Rename to ...
	* gdb.threads/signal-while-stepping-over-bp-other-thread.c: ... this.
	* gdb.threads/step-after-sr-lock.exp: Rename to ...
	* gdb.threads/signal-while-stepping-over-bp-other-thread.exp:
	... this.