add support for atomic operation instructions

This adds support for the atomic load-link/store-conditional
instruction l.lwa and l.swa.
In addition to that, tests that ensure their correct behaviour
are also added.

* ChangeLog:

2014-05-04  Stefan Kristiansson  <stefan.kristiansson@saunalahti.fi>

	* cpu/common/abstract.c:
	(set_mem32) Clear atomic reserve on write to atomic address.
	(set_mem16) Likewise.
	(set_mem8) Likewise.
	* cpu/common/execute.h <cpu_state>: Add loadlock_active and
	loadlock_address members.
	* cpu/or1k/except.c (except_handle): Clear atomic reserve on
	exceptions.
	* cpu/or32/insnset.c:
	(l_swa): New function.
	(l_lwa): Likewise.
	* cpu/or32/or32.c <or1ksim_or32_opcodes>: Add l.lwa and l.swa
	instructions.
	* cpu/or32/simpl32-defs.h: Add l_swa and l_lwa declarations.
	* cuc/load.c <conv>: Add l.lwa and l.swa instructions.

* testsuite/ChangeLog:

2014-05-04  Stefan Kristiansson  <stefan.kristiansson@saunalahti.fi>

	* or1ksim.tests/atomic.exp: New file. Test for atomic
	(l.lwa/l.swa) instructions.

* testsuite/test-code-or1k/ChangeLog:

2014-05-04  Stefan Kristiansson  <stefan.kristiansson@saunalahti.fi>

	* atomic: New directory. Tests for l.lwa and l.swa atomic
 			instructions.
	* atomic/atomic.S: New file.
	* atomic/Makefile.in: Likewise.
	* atomic/Makefile.am: Likewise.
	* Makefile.am: Add atomic test.
	* configure.ac: Likewise.
	* Makefile.in: Regenerated.
	* configure: Likewise.