NaCl: Update revision in DEPS, b6ec17d -> a0559c4

NaCl: Update revision in DEPS, b6ec17d -> a0559c4

This pulls in the following Native Client changes:

82dc370: (mseaborn@chromium.org) Cleanup: Remove NACL_PROT_* #defines; use NACL_ABI_PROT_* instead
d820a72: (mseaborn@chromium.org) Cleanup: Remove NaClDesc's UnmapUnsafe() method
3626eb5: (mcgrathr@chromium.org) elf_loader: code_data_alloc bookkeeping for dyncode_create fallback
c328372: (mcgrathr@chromium.org) toolchain_build: Update glibc revision
cdb63df: (mcgrathr@chromium.org) Deploy new nacl_arm_glibc toolchain
8191980: (mseaborn@chromium.org) Cleanup: Merge NaClDescUnmapUnsafe() and NaClHostDescUnmapUnsafe()
9a6bdda: (mcgrathr@chromium.org) Use native tar rather than gnutar to download glibc on Mac
7c3b0d2: (mcgrathr@chromium.org) Avoid -ledit dependency in PNaCl toolchain build
c2e3d24: (mseaborn@chromium.org) Cleanup: De-duplicate code for converting mprotect() prot flags
3f81c4b: (mseaborn@chromium.org) PNaCl: Update nacl-newlib revision in pnacl/COMPONENT_REVISIONS: timezone decl
a0559c4: (mcgrathr@chromium.org) Update revision for PNaCl

Changes: https://chromium.googlesource.com/native_client/src/native_client/+log/b6ec17db8c2958f3455043e29000f17354336fb8..a0559c4cc7e9f95b41982a8f4ba10a04173c6c75

BUG=560295
TEST=browser_tests and nacl_integration
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:linux_chromium_dbg_32_ng,linux_arm_compile,linux_nacl_sdk_build;tryserver.chromium.mac:mac_chromium_10.6_rel_ng
R=magjed@chromium.org, mseaborn@chromium.org, sbc@chromium.org

Committed: https://crrev.com/b7a28ee46bd17bc68b34b8f554dbafee11f9f8f6
Cr-Commit-Position: refs/heads/master@{#361420}

[Mark Seaborn, 2015-11-24 18:24:34]

Auto-LGTM

[Roland McGrath, 2015-11-24 18:32:21]

The CQ bit was checked by mcgrathr@chromium.org

[commit-bot: I haz the power, 2015-11-24 18:36:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1474713003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1474713003/1

[commit-bot: I haz the power, 2015-11-24 20:06:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-24 20:06:55]

Patchset 1 (id:??) landed as
https://crrev.com/b7a28ee46bd17bc68b34b8f554dbafee11f9f8f6
Cr-Commit-Position: refs/heads/master@{#361420}