* win32-nat.c (safe_symbol_file_add_cleanup): Ensure that gdb_stderr is flushed

* win32-nat.c (safe_symbol_file_add_cleanup): Ensure that gdb_stderr is flushed
before deleting and restoring it.
(safe_symbol_file_add): Ensure that gdb_stderr is flushed before reassigning
it.
(handle_load_dll): Split into two functions so that WFI can handle shared
library events.
(child_solib_loaded_library_pathname): New function.
(child_clear_solibs): New function.  Clears shared library list.
(child_solib_add): New function.  Adds shared library symbols.
(dll_symbol_command): New function.  Handles "dll-symbol" command.
(info_dll_command): New function.  Handles info "sharedlibrary" command.
(handle_exceptions): Eliminate 'ignore_trap' argument.
(get_child_debug_event): Eliminate two arguments.  Return "pid" when
appropriate.  Break out on most events to allow WFI to handle stuff.
(child_wait): Accomodate get_child_debug_event changes.
(child_attach): Clear thread list and list of loaded dlls.
(child_create_inferior): Clear list of loaded dlls.  Use wait_for_inferior in a
loop to look for first "trap".
(child_resume): Avoid accessing a possibly-freed thread pointer.
(_initialize_inftarg): Add "dll-symbols", "sharedlibrary", and "info
dll", and "info sharedlibrary" commands.
* config/i386/tm-cygwin.h: Add some shared library (aka DLL) hooks.