increase MAXTSIZ for m68k in order to run GCC 5.4

[Rin Okuyama <rokuyama%rk.phys.keio.ac.jp@localhost>]

GCC 5.4 fails to run on a m68k machine:

  % uname -mpr
  7.99.42 x68k m68k
  % cc hello.c
  check_exec: rejecting due to limits (t=9358872 > 8388608 || d=1104212 > 16777216)
  cc: error trying to exec '/usr/libexec/cc1': execv: Cannot allocate memory

This is due to text size of cc1 (~ 9MB) is larger than MAXTSIZ (= 8MB).
Is it OK to increase the default value for m68k ports? If so, how large
should it be? Is 16MB acceptable?

Thanks,
Rin