gcd: files for GCD dispatcher (right now just copy of OMP one), add items to glViewer
gcd: naive implementation using dispatch_apply for all loops. Not faster, dispatch overhead too high
gcd: convert most of loops to submit work in 32 item size batches.
MBP6,2 (2 core 4 thread), catmark_car Lv3: 6.9ms CPU, 5.2ms GCD; Lv4: 31.2ms CPU, 22.ms GCD
gcd: convert face loop to work in 32 item size batches.
MBP6,2 (2 core 4 thread), catmark_car Lv4: 31.2ms CPU, 15.8ms GCD (was 22ms)
gcd: cleanup CMakeLists
gcd: cleanup
Merge pull request #106 from aras-p/gcd

Implement Apple GCD dispatcher