GCC 7 Support

[David Michael]

Hi,

Can a linux/src/include/linux/compiler-gcc7.h be added to gnumach?  I
just ran the following since the versioned compiler headers were
dropped upstream ~4.2.

    sed s/gcc6/gcc7/g < compiler-gcc6.h > compiler-gcc7.h

It also needed __udivmoddi4 added to clib_routines in gnumach's Makefile.am.

Side note:  I couldn't bootstrap cross-compilers with
tschwinge/Roger_Whittaker since the last proc defs changes.  Is there
a more current branch somewhere?

Thanks.

David