types

The type which probably started as a real enum of possible post filtering
options now also includes options used for compilers' invocations.

The type was already split, but the naming was not reflecting this in the other
part of the code.

This changes tries to apply a simple renaming to the type only (corresponding
variables are left as 'filters').

While doing so, some typing error were discovered around the GccDump feature.
A fix for this will follow in a different PR.

Signed-off-by: Marc Poulhiès <dkm@kataplop.net>