Travis: Fail fast, disable JIT for functional tests.

Disable JIT to find cause for random `PANIC: unprotected error in call to Lua API` on Travis (OS X).

.travis.yml

@@ -28,6 +28,7 @@ matrix:
     - os: osx
       env: CI_TARGET=gcc
       compiler: gcc-4.9
+  fast_finish: true
 before_install:
   # Pins the version of the java package installed on the Travis VMs
   # and avoids a lengthy upgrade process for them.

test/functional/helpers.lua

@@ -1,3 +1,8 @@
+if jit then
+  -- Disable JIT because of random errors on Travis with OS X.
+  jit.off(true, true)
+end
+
 require('coxpcall')
 local Loop = require('nvim.loop')
 local MsgpackStream = require('nvim.msgpack_stream')