Build: Remove bashism from configure

Patrick Welche reported that the FoX configure
script uses '==' for string comparison instead
of the portable '='. This comes from our local
copy of autoconf's fortran.m4. Fix this, and
regenerate the configure script.

This closes issue andreww#29.

config/aclocal.m4

@@ -4799,7 +4799,7 @@ AC_CACHE_CHECK([whether $FPP fulfils requested features],
 
   ac_cv_fpp_build_rule=indirect
 
-if test ac_fpp_ok == no; then
+if test ac_fpp_ok = no; then
   AC_MSG_ERROR([Cannot find a Fortran preprocessor with the requested features])
 fi
 

config/m4/fortran.m4

@@ -3107,7 +3107,7 @@ AC_CACHE_CHECK([whether $FPP fulfils requested features],
 
   ac_cv_fpp_build_rule=indirect
 
-if test ac_fpp_ok == no; then
+if test ac_fpp_ok = no; then
   AC_MSG_ERROR([Cannot find a Fortran preprocessor with the requested features])
 fi
 

configure

@@ -4781,7 +4781,7 @@ echo "${ECHO_T}$ac_cv_prog_fpp_ok" >&6; }
 
   ac_cv_fpp_build_rule=indirect
 
-if test ac_fpp_ok == no; then
+if test ac_fpp_ok = no; then
   { { echo "$as_me:$LINENO: error: Cannot find a Fortran preprocessor with the requested features" >&5
 echo "$as_me: error: Cannot find a Fortran preprocessor with the requested features" >&2;}
    { (exit 1); exit 1; }; }