PR144 (aligned patchers on x86_64)

PR144 (aligned patchers on x86_64)
* src/vm/jit/patcher-common.cpp,
src/vm/jit/patcher-common.h (patchref_t): Added
yet another field - patch_align.
* src/vm/jit/x86_64/codegen.c, src/vm/jit/x86_64/codegen.h:
Make all patched code instances aligned.
* src/vm/jit/x86_64/emit.c (emit_arbitrary_nop): Added.
* src/vm/jit/x86_64/emit.h: Likewise.
* src/vm/jit/x86_64/patcher.c: Adapted to new code layout,
verify alignment.
* tests/regression/bugzilla/PR144.java: Added new test case
exercising the new code paths.
* tests/regression/bugzilla/All.java: Likewise.