Remove typdefs for pointer types in fx_system.h.

This involves fixing some multiple variable per line
declarations, as the textually-substituted "*" applies
only to the first one.

This involves moving some consts around following the
substitution.

This involves replacing some typedefs used as constructors
with better code.

R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1171733003