Removed unused GlobalVariable declarations

Cleaned up the code by removing some GlobalVariable declarations that
are never assigned to.  (These have long since been replaced by the
mem_insts_var array.)
Made remove_files ignore nonexistent files

Modified the remove_files subroutine to ignore any files that do not
actually exist.  This is needed to avoid aborting when -save-temps is
used with -bf-disable=byfl, as not all temporary files are created in
that case.
Tally branch ops

Added code to tally unconditional and conditional branches even in the
absence of -bf-every-bb.