Fix gdb 8.1 Solaris compilation

I just tried to compile gdb trunk on Solaris 11.4 (formerly 12), and
failed for a couple of reasons:

*

In file included from /usr/include/python2.7/Python.h:128:0,
                 from /vol/src/gnu/gdb/gdb/dist/gdb/python/python-internal.h:94,
                 from /vol/src/gnu/gdb/gdb/dist/gdb/python/py-instruction.h:23,
                 from /vol/src/gnu/gdb/gdb/dist/gdb/python/py-instruction.c:21:
/usr/include/python2.7/ceval.h:67:0: error: ignoring #pragma no_inline  [-Werror=unknown-pragmas]
 #pragma no_inline(PyEval_EvalFrameEx)
 ^

  New in Solaris 11.4: <python2.7/ceval.h> uses a Studio-only #pragma.
  I've disabled the warning in warnings.m4.

*

/vol/src/gnu/gdb/gdb/dist/gdb/ser-pipe.c: In function ‘int pipe_open(serial*, const char*)’:
/vol/src/gnu/gdb/gdb/dist/gdb/ser-pipe.c:77:9: error: ‘pid_t vfork()’ is deprecated (declared at /usr/include/unistd.h:659) [-Werror=deprecated-declarations]
   pid = vfork ();
         ^
/vol/src/gnu/gdb/gdb/dist/gdb/ser-pipe.c:77:16: error: ‘pid_t vfork()’ is deprecated (declared at /usr/include/unistd.h:659) [-Werror=deprecated-declarations]
   pid = vfork ();
                ^

  Since Solaris 11, vfork () is marked deprecated in <unistd.h>.

  cf. vfork(2):

       The  vfork()  and vforkx() functions are deprecated. Their sole legiti-
       mate use as a prelude to an immediate call to a function from the  exec
       family can be achieved safely by posix_spawn(3C) or posix_spawnp(3C).

  Again, I've disabled the warning.

*

/vol/src/gnu/gdb/gdb/dist/gdb/cli/cli-cmds.c: In function ‘void shell_escape(const char*, int)’:
/vol/src/gnu/gdb/gdb/dist/gdb/cli/cli-cmds.c:750:14: error: ‘pid_t vfork()’ is deprecated (declared at /usr/include/unistd.h:659) [-Werror=deprecated-declarations]
   if ((pid = vfork ()) == 0)
              ^
/vol/src/gnu/gdb/gdb/dist/gdb/cli/cli-cmds.c:750:21: error: ‘pid_t vfork()’ is deprecated (declared at /usr/include/unistd.h:659) [-Werror=deprecated-declarations]
   if ((pid = vfork ()) == 0)
                     ^

  Same problem.

*

/vol/src/gnu/gdb/gdb/dist/gdb/procfs.c: In function ‘void procfs_init_inferior(target_ops*, int)’:
/vol/src/gnu/gdb/gdb/dist/gdb/procfs.c:4380:30: error: ‘START_INFERIOR_TRAPS_EXPECTED’ was not declared in this scope
   gdb_startup_inferior (pid, START_INFERIOR_TRAPS_EXPECTED);
                              ^

  defined in nat/fork-inferior.h, need to include that header

/vol/src/gnu/gdb/gdb/dist/gdb/procfs.c: In function ‘void procfs_create_inferior(target_ops*, const char*, const string&, char**, int)’:
/vol/src/gnu/gdb/gdb/dist/gdb/procfs.c:4605:38: error: ‘fork_inferior’ was not declared in this scope
          NULL, NULL, shell_file, NULL);
                                      ^

  likewise

/vol/src/gnu/gdb/gdb/dist/gdb/procfs.c: In function ‘void procfs_info_proc(target_ops*, const char*, info_proc_what)’:
/vol/src/gnu/gdb/gdb/dist/gdb/procfs.c:5124:20: error: ‘argv’ was not declared in this scope
   for (char *arg : argv)
                    ^

  Typo, should be built_argv instead!

*

Undefined                       first referenced
 symbol                             in file
fork_inferior(char const*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, char**, void (*)(), void (*)(int), void (*)(), char const*, void (*)(char const*, char* const*, char* const*)) procfs.o
startup_inferior(int, int, target_waitstatus*, ptid_t*) fork-child.o
ld: fatal: symbol referencing errors
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:2249: gdb] Error 1

  Need to add fork-inferior.o to NATDEPFILES.

With the changes below, I can build gdb on sparcv9-sun-solaris2.11 and
amd64-pc-solaris2.11 and a simple smoke test (gdb/gdb gdb/gdb) works.

gdb/configure

@@ -15155,10 +15155,17 @@ build_warnings="-Wall -Wpointer-arith \
 -Wno-sign-compare -Wno-narrowing -Wno-error=maybe-uninitialized \
 -Wno-mismatched-tags"
 
-# Enable -Wno-format by default when using gcc on mingw since many
-# GCC versions complain about %I64.
 case "${host}" in
-  *-*-mingw32*) build_warnings="$build_warnings -Wno-format" ;;
+  *-*-mingw32*)
+    # Enable -Wno-format by default when using gcc on mingw since many
+    # GCC versions complain about %I64.
+    build_warnings="$build_warnings -Wno-format" ;;
+  *-*-solaris*)
+    # Solaris 11.4 <python2.7/ceval.h> uses #pragma no_inline that GCC
+    # doesn't understand.
+    build_warnings="$build_warnings -Wno-unknown-pragmas"
+    # Solaris 11 <unistd.h> marks vfork deprecated.
+    build_warnings="$build_warnings -Wno-deprecated-declarations" ;;
   *) build_warnings="$build_warnings -Wformat-nonliteral" ;;
 esac