[OpenCL] Use long instead of long long in x86 builtins

Summary: According to C99 standard long long is at least 64 bits in
size. However, OpenCL C defines long long as 128 bit signed
integer. This prevents one to use x86 builtins when compiling OpenCL C
code for x86 targets. The patch changes long long to long for OpenCL
only.

Patch by: Alexander Batashev <alexander.batashev@intel.com>

Reviewers: craig.topper, Ka-Ka, eandrews, erichkeane, Anastasia

Reviewed By: Ka-Ka, erichkeane, Anastasia

Subscribers: a.elovikov, yaxunl, Anastasia, cfe-commits, ivankara, etyurin, asavonic

Tags: #clang

Differential Revision: https://reviews.llvm.org/D62580

llvm-svn: 362391