Add support for a simple "miniperf" format, decoded with pure Python.
Switch run-sps.sh record-sps to use miniperf; expose it directly as well.
Switch default manifest branch.
Recognize Mac hosts for B2G_PROFILING and run-perf
Elfhack-proof perf-to-sps.
Move perf profiling env setup into load-config, so run-perf.sh can use it.
Revert "Switch default manifest branch."; the manifests have been merged.

This reverts commit 262ee8e5535350d5febd9c17b7871af9cac14996.
Merge branch 'miniperf' into profiling