disable qthreads internal spinlocks for pgi/PrgEnv-pgi

pgi doesn't support the proper atomic intrinsics that are required for
spinlocks to be fast, so disable them for pgi, and PrgEnv-pgi
look for substring pgi in target_compiler instead of explicit match

Greg suggested doing this to make it more robust against future compiler name
changes and that it makes it easier to read (both of which I agree with)
Merge pull request #299 from ronawho/qthreads-timeouts

disable qthreads internal spinlocks for pgi/PrgEnv-pgi

[reviewed by @gbtitus]

pgi doesn't support the proper atomic intrinsics that are required for
spinlocks to be fast, so disable them for pgi, and PrgEnv-pgi