This patch implements Flow Sensitive Sample FDO (FSAFDO). It has the following
(1) disable current discriminator coding scheme.
(2) new hierarchical discriminator for FSAFDO
(3) FSAFDO profile loader.
For this patch, "-enable-fs-discriminator=true" turns on the new functionality.
"-enable-fs-discriminator=false" (the default) keeps current Sample FDO behavior.
This patch is not intended for check-in. I post it mainly to get the advises on to break
into smaller patches. Also because of this, I did not include the test cases.