gfortran: remove conflicting info pages
Disable make_fuss when running configure invoked by make

The cc wrapper's make_fuss is only enabled when HOMEBREW_CCCFG contains
'O', which is set by the make wrapper. This means it is disable when
running configure scripts. However, this does not include configure
scripts invoked by make, which inherit the value of HOMEBREW_CCCFG from
the make process. make_fuss will be enabled for these scripts, cause
breakage.

Configure scripts generated by autoconf 2.56 (November 2002) or later
export DUALCASE into the environment of subprocesses. This variable is
only used by the MKS shell, so we can use it as a heuristic to determine
if we are running as a subprocess of a configure script.