Ensure function.end_line in source_info.lines

Ensure function.end_line in source_info.lines

Ensure that the function.end_line in the lines vector for the source
file, even if it is not explicitly touched by a basic block. This
ensures consistency with what you would expect. For example, this file
has sources[sum.cc].lines.size () == 23 and main.end_line == 2 without
adjusting sources.lines, which in this case is a no-op.

    #####:   17:int main ()
        -:   18:{
    #####:   19:  sum (1, 2);
    #####:   20:  sum (1.1, 2);
    #####:   21:  sum (2.2, 2.3);
    #####:   22:}

This is a useful property when combined with selective reporting.

gcc/ChangeLog:

	* gcov.cc (process_all_functions): Ensure fn.end_line is
	included source[fn].lines.