Add NaCl OS ABI to enumeration.

BUG= http://code.google.com/p/nativeclient/issues/detail?id=2774
TEST= none

R=eaeltsin@google.com

Review URL: https://chromiumcodereview.appspot.com/10407091
diff --git a/gdb/defs.h b/gdb/defs.h
index e4c2483..75cfcb2 100644
--- a/gdb/defs.h
+++ b/gdb/defs.h
@@ -915,6 +915,7 @@
   GDB_OSABI_DICOS,
   GDB_OSABI_DARWIN,
   GDB_OSABI_SYMBIAN,
+  GDB_OSABI_NACL,
 
   GDB_OSABI_INVALID		/* keep this last */
 };
diff --git a/gdb/osabi.c b/gdb/osabi.c
index aba9842..6717737 100644
--- a/gdb/osabi.c
+++ b/gdb/osabi.c
@@ -72,6 +72,7 @@
   "DICOS",
   "Darwin",
   "Symbian",
+  "NaCl",
 
   "<invalid>"
 };