The original implementation had the statistics system woken very
tightly into things like PPCallbacks, with counters duplicated
in two places, and all the output code duplicated. This made it
very difficult to alter the structure of the program without
breaking the statistics system.
Since the planned approach for solving the remaining preprocessor
bugs needs the introduction of a custom FrontendAction, and such
a restructure was incompatible with the way the statistics system
was set up, this rewrite was required.
'tis rather simpler now, mind you :D
This commit also fixes an issue where some stats were counted
twice, and allows `-print-stats` to operate independently of
`-stat-output`, allowing you to print stats to a file without
printing them to a terminal (or vice-versa).
[ROCm/clr commit: dd5a60054a]
Chris Kitching
4e6ca773fa