Autoconf fix Darwin/MacOS X Fortran

[Bill Northcott]

In lib/autoconf/fortran.m4  (v2.60 and cvs) there is a macro  
_AC_FC_LIBRARY_LDFLAGS which  defines FLIBS for linking Fortran code.

Around line 664 is
          # Ignore these flags.
        -lang* | -lcrt*.o | -lc | -lgcc | -libmil | -LANG:=* | - 
LIST:* | -LNO:*)

Darwin/MacOS X also include elements of the C library in  
libgcc_s.dylib and libSystem.dylib.  While including -lSystem in the  
link command seems to be harmless, including -lgcc_s can cause large  
links to fail.  Neither is necessary because ld automatically  
includes them.

The problems are fixed by changing the above lines to:
          # Ignore these flags.
        -lang* | -lcrt*.o | -lc | -lgcc* | -lSystem | -libmil | - 
LANG:=* | -LIST:* | -LNO:*)

I would not expect this to cause problems on other platforms, but I  
can't test it.

Regards
Bill Northcott