[pph] Remove all the -fpph flags and pph_catch_... calls that instrumented the incr compiler (issue4559070)

[Gabriel Charette]

(sorry about the triple-posting, just learnt this mailing list
required plain text emails... hopefully, this works now..)

Additional note: The patch was tested with a full bootstrap build and
regression testing (no new bugs introduced).

There might be header files that are now unused due to the code removed.

-Gab