NaCl: Update revision in DEPS, r6736 -> r6743

This pulls in the following Native Client changes:

r6737: (khim) Partial rollback of r6734.
r6738: (mcgrathr) Add gyp/scons configury and buildbot option to build trusted code with Clang
r6739: (jvoung) Update llvm/llvm-gcc revs to pull in trivial merge
r6740: (mcgrathr) Roll back gtest_rev 364
r6741: (mcgrathr) Make Mac clang bot 32-bit
r6742: (kschimpf) Speed up x86-64 validator by inlining buffer segment reads. Speeds up x86-64 validator by approximately 11%.
r6743: (kschimpf) Speed up x86-64 validator by inlining heavily called routines. Speeds up

BUG=none
TEST=nacl_integration


Review URL: http://codereview.chromium.org/7977028

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@102194 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -7,7 +7,7 @@ vars = {
   "webkit_revision": "95596",
   "chromium_git": "http://git.chromium.org/git",
   "swig_revision": "69281",
-  "nacl_revision": "6736",
+  "nacl_revision": "6743",
   # After changing nacl_revision, run 'glient sync' and check native_client/DEPS
   # to update other nacl_*_revision's.
   # TODO(brettw) We should use the "From" syntax to avoid hardcoding the