New autoconf fails to handle our fortran.m4

[andreww]

The current version of autoconf (2.65) does not seem to like our local version of fortran.m4 (which adds pre-processed fortran as a language - this never made it upstream). Fails with:

autoconf
configure.ac:19: error: AC_LANG_CONFTEST: unknown language: Preprocessed Fortran
../../lib/autoconf/lang.m4:194: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2557: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2573: AC_COMPILE_IFELSE is expanded from...
aclocal.m4:3198: _AC_FPP_FIXEDFORM_F is expanded from...
aclocal.m4:4291: _AC_PROG_FC_CPP is expanded from...
aclocal.m4:4634: AC_PROG_FPP is expanded from...
configure.ac:19: the top level

... Looks like the way languages are defined has changed. (Autoconf 2.59 (the older version on debian sid) mostly works, but this pre-dates the mkdir -p macro so this fails for another reason.)