Remove some uses of TUI_WIN_SRC

Remove some uses of TUI_WIN_SRC

This adds a 'win_info' parameter to a couple of functions.  This
reduces the number of references to the TUI_WIN_SRC global.

gdb/ChangeLog
2019-07-17  Tom Tromey  <tom@tromey.com>

	* tui/tui-winsource.c (tui_update_source_window_as_is)
	(tui_update_source_windows_with_addr): Update.
	* tui/tui-source.h (tui_set_source_content)
	(tui_show_symtab_source): Add "win_info" parameter.
	* tui/tui-source.c (tui_set_source_content): Add "win_info"
	parameter.
	(tui_show_symtab_source): Likewise.