NaCl: Remove PNaCl's IRT interface whitelist from the PNaCl IRT shims

Disabling various IRT interfaces under PNaCl is now done in the NaCl
repo by irt_interfaces.c, as long as pnacl_mode is set to true in
nacl_listener.cc.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3803
TEST=PnaclExceptionHandlingDisabled, PnaclDyncodeSyscallDisabled
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/191503002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255799 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255799