Document language choice in 'info [functions|variables|types]|rbreak' commands

doc/ChangeLog
2018-11-20  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* gdb.texinfo (Examining the Symbol Table): Document language choice
	for 'info types|functions|variables' commands.
	(Setting Breakpoints): Document language choice to print
	the functions in which a breakpoint is set.