* win32-nat.c (CYGWIN_SIGNAL_STRING): Delete.

* win32-nat.c (CYGWIN_SIGNAL_STRING): Delete.
(_CYGWIN_SIGNAL_STRING): Define if not already defined in cygwin.h.
(win32_add_thread): Use XZALLOC rather than xmalloc/memset.
(register_loaded_dll): Ditto.
(handle_load_dll): Call solib_add here.
(handle_unload_dll): Ditto.
(info_dll_command): Delete.
(handle_output_debug_string): Use official _CYGWIN_SIGNAL_STRING.
(win32_current_sos): Duplicate table to pass off to caller rather than deleting
our version.
(set_win32_aliases): New function.
(_initialize_win32_nat): Remove local handling of "info shared".  Set
deprecated_init_ui_hook to allow late setting of "info dll" alias.