coccinelle: implement parallel check

This patch is an implementation of parallel check of files. It uses
GNU parallel to run multiple spatch at once.
The concurrency level is set via the CONCURRENCY_LEVEL environment
variable.
locks: clean up locks declarations

Split threads.h into several files, where each of these files defines
all lock types and macro's.

threads.h defines the normal case
threads-debug.h defines the debug variants
threads-profile.h defines the lock profiling variants

Finally, threads-arch-tile.h moves the Tilera specifics out