Remove duplicate or commented-out #includes

I wrote a little script to detect duplicate or commented-out #includes
and ran it on gdb.  This patch is the result.  Tested by rebuilding.

gdb/ChangeLog
2019-01-21  Tom Tromey  <tom@tromey.com>

	* ui-out.c: Fix includes.
	* tui/tui-source.c: Fix includes.
	* target.c: Fix includes.
	* remote.c: Fix includes.
	* regcache.c: Fix includes.
	* python/py-block.c: Fix includes.
	* printcmd.c: Fix includes.
	* or1k-tdep.c: Fix includes.
	* mi/mi-main.c: Fix includes.
	* m32r-tdep.c: Fix includes.
	* csky-tdep.c: Fix includes.
	* compile/compile-cplus-types.c: Fix includes.
	* cli/cli-interp.c: Fix includes.

gdb/gdbserver/ChangeLog
2019-01-21  Tom Tromey  <tom@tromey.com>

	* tracepoint.c: Fix includes.
	* remote-utils.c: Fix includes.
	* linux-x86-low.c: Fix includes.

gdb/stubs/ChangeLog
2019-01-21  Tom Tromey  <tom@tromey.com>

	* ia64vms-stub.c: Fix includes.

gdb/python/py-block.c

@@ -23,7 +23,6 @@
 #include "symtab.h"
 #include "python-internal.h"
 #include "objfiles.h"
-#include "symtab.h"
 
 typedef struct blpy_block_object {
   PyObject_HEAD