OpenCL 1.1 does not define CL_VERSION_1_2 so use hardcoded number instead

Otherwise the test evaluates to true on OpenCL 1.1 and earlier. Since we
therefore cannot use the CL_VERSION_?_? macros move them to the proper
position in the top-level header.


git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@211787 91177308-0d34-0410-b5e6-96231b3b80d8