NaCl: Update revision in DEPS, r11963 -> r11979

NaCl: Update revision in DEPS, r11963 -> r11979

This pulls in the following Native Client changes:

r11964: (sbc) Add IRT interface for new syscalls (chdir/mkdir/rmdir/etc)
r11965: (jfb) Add pthread_mutex_timedlock.
r11966: (jfb) Test C++11 <thread> for PNaCl
r11967: (jfb) Update PNaCl DEPS
r11968: (khim) Update gcc revision in tools/REVISIONS
r11969: (halyavin) Update toolchain revision.
r11970: (halyavin) Enable base address hiding for PNaCl gdb tests.
r11971: (jfb) Update TOOL_REVISIONS for PNaCl 11956->11967
r11972: (jvoung) Adjust perf_expectations for perf_improve (mostly transfersize, some runtime).
r11973: (mseaborn) Thread suspension: Enable stress test for context switches on ARM
r11974: (phosek) Consistent mprotect behavior across all platforms
r11975: (jvoung) Remove old experimental pnacl_ld_experiments.
r11976: (eliben) Prune more unused stuff when building the PNaCl toolchain
r11977: (bradnelson) Pulling in different glibc revision.
r11978: (stichnot) Allow testing non-default clang/llc optimization settings.
r11979: (bradnelson) Allowing r/w PT_DYNAMIC in addition to r-only.

BUG=none
TEST=browser_tests and nacl_integration