-m64 fixed on Solaris 2.7 !!

[Igor Schein]

Hi,

I finally figured out how to reactivate capability to build 64bit
binaries on Solaris 2.7.  There're 2 things.  First, here's the key
line:  

% sed -n 3108p gcc/config.gcc
# At the moment, 32-to-64 cross compilation doesn't work.

The whole section below it is commented out.  Someone observed that
building dual-arch compiler fails and disabled it altogether.  So I
went back and eventually found this:

revision 1.7883
date: 2000/09/26 14:14:31;  author: jakub;  state: Exp;  lines: +8 -0
        * config/sparc/sparc.c (sparc_emit_set_const64): Don't abort when
        op0 is a SUBREG.
        (function_arg_slotno): Accept TImode/CTImode.
        * config/sparc/sparc.h (MIN_UNITS_PER_WORD): If IN_LIBGCC2 define
        to UNITS_PER_WORD.

This is the change which started failing bootstrap in the first place.
Reverting it enabled me to build a working 64-bit gcc-2.97 compiler.
Attached is the patch which summarized the above changes required to
hack things into working ( applicable to the current tree ).  However,
I'd greatly appreciate if Jakub could find some time at some point to
review his Sep 26 change and adjust it to properly re-enable 64bit
compiling in the main tree,since I'm not qualified to do that.  I'm
sure I'm not alone in asking this.  

Thanks

Igor