Remove unused includes in ada-*.c files

Remove unused includes in ada-*.c files

include-what-you-use reports:

../../../src/binutils-gdb/gdb/ada-lang.c should remove these lines:
- #include <sys/stat.h>  // lines 43-43
- #include <map>  // lines 66-66
- #include "c-lang.h"  // lines 33-33
- #include "demangle.h"  // lines 23-23
- #include "dictionary.h"  // lines 47-47
- #include "gdbsupport/gdb_vecs.h"  // lines 53-53
- #include "psymtab.h"  // lines 58-58

../../../src/binutils-gdb/gdb/ada-lang.c should remove these lines:
- #include <sys/stat.h>  // lines 43-43
- #include <map>  // lines 66-66
- #include "c-lang.h"  // lines 33-33
- #include "demangle.h"  // lines 23-23
- #include "dictionary.h"  // lines 47-47
- #include "gdbsupport/gdb_vecs.h"  // lines 53-53
- #include "psymtab.h"  // lines 58-58

../../../src/binutils-gdb/gdb/ada-valprint.c should remove these lines:
- #include "c-lang.h"  // lines 31-31
- #include "demangle.h"  // lines 26-26
- #include "infcall.h"  // lines 32-32
- #include "objfiles.h"  // lines 33-33
- #include "symtab.h"  // lines 22-22

Remove these includes.  Adding an include for gdbarch.h in
ada-valprint.c was necessary, because gdbarch_byte_order wouldn't be
found anymore.

gdb/ChangeLog:

	* ada-lang.c: Remove includes.
	* ada-typeprint.c: Remove includes.
	* ada-valprint.c: Remove includes.

Change-Id: I07c2f2237ef0ed5fd9aa855d33711d780794fce2