Bug#846507: the D frontend fails to build on sparc64

[Matthias Klose <doko@debian.org>]

Package: src:gcc-7
Version: 7-20161201-1
Severity: important

See
https://buildd.debian.org/status/fetch.php?pkg=gcc-7&arch=sparc64&ver=7-20161201-1&stamp=1480609625

GDC trunk is a snapshot from 20161113

In file included from ./tm_p.h:4:0,
                 from ../../src/gcc/d/d-target.cc:33:
../../src/gcc/config/sparc/sparc-protos.h:50:47: error: use of enum 'memmodel'
without previous declaration
 extern void sparc_emit_membar_for_model (enum memmodel, int, int);
                                               ^~~~~~~~
Makefile:1101: recipe for target 'd/d-target.o' failed
make[5]: *** [d/d-target.o] Error 1
make[5]: *** Waiting for unfinished jobs....
../../src/gcc/d/d-glue.cc: In function 'void escapePath(OutBuffer*, const char*)':
../../src/gcc/d/d-glue.cc:289:24: warning: this statement may fall through
[-Wimplicit-fallthrough=]
    buf->writeByte('\\');
                        ^
../../src/gcc/d/d-glue.cc:291:2: note: here
  default:
  ^~~~~~~