Use nat/windows-nat function indirection code

Use nat/windows-nat function indirection code

This changes gdbserver to use the function indirection code that was
just moved into nat/windows-nat.[ch].  One additional function is used
by gdbserver that was not used by gdb.

gdb/ChangeLog
2021-04-30  Tom Tromey  <tromey@adacore.com>

	* nat/windows-nat.h (GenerateConsoleCtrlEvent): New define.
	(GenerateConsoleCtrlEvent_ftype, GenerateConsoleCtrlEvent):
	Declare.
	* nat/windows-nat.c (GenerateConsoleCtrlEvent): Define.
	(initialize_loadable): Initialize GenerateConsoleCtrlEvent.

gdbserver/ChangeLog
2021-04-30  Tom Tromey  <tromey@adacore.com>

	* win32-low.cc (GETPROCADDRESS): Remove.
	(winapi_DebugActiveProcessStop, winapi_DebugSetProcessKillOnExit)
	(winapi_DebugBreakProcess, winapi_GenerateConsoleCtrlEvent)
	(winapi_Wow64SetThreadContext, win32_Wow64GetThreadContext)
	(win32_Wow64SetThreadContext): Remove.
	(win32_set_thread_context, do_initial_child_stuff)
	(win32_process_target::attach, win32_process_target::detach):
	Update.
	(winapi_EnumProcessModules, winapi_EnumProcessModulesEx)
	(winapi_GetModuleInformation, winapi_GetModuleInformationA):
	Remove.
	(win32_EnumProcessModules, win32_EnumProcessModulesEx)
	(win32_GetModuleInformation, win32_GetModuleInformationA):
	Remove.
	(load_psapi): Remove.
	(win32_add_dll, win32_process_target::request_interrupt): Update.
	(initialize_low): Call initialize_loadable.