gcov: branch, conds, calls in function summaries

gcov: branch, conds, calls in function summaries

The gcov function summaries only output the covered lines, not the
branches and calls. Since the function summaries is an opt-in it
probably makes sense to also include branch coverage, calls, and
condition coverage.

$ gcc --coverage -fpath-coverage hello.c -o hello
$ ./hello

Before:
    $ gcov -f hello
    Function 'main'
    Lines executed:100.00% of 4

    Function 'fn'
    Lines executed:100.00% of 7

    File 'hello.c'
    Lines executed:100.00% of 11
    Creating 'hello.c.gcov'

After:
    $ gcov -f hello
    Function 'main'
    Lines executed:100.00% of 3
    No branches
    Calls executed:100.00% of 1

    Function 'fn'
    Lines executed:100.00% of 7
    Branches executed:100.00% of 4
    Taken at least once:50.00% of 4
    No calls

    File 'hello.c'
    Lines executed:100.00% of 10
    Creating 'hello.c.gcov'

    Lines executed:100.00% of 10

With conditions:
    $ gcov -fg hello
    Function 'main'
    Lines executed:100.00% of 3
    No branches
    Calls executed:100.00% of 1
    No conditions

    Function 'fn'
    Lines executed:100.00% of 7
    Branches executed:100.00% of 4
    Taken at least once:50.00% of 4
    Condition outcomes covered:100.00% of 8
    No calls

    File 'hello.c'
    Lines executed:100.00% of 10
    Creating 'hello.c.gcov'

    Lines executed:100.00% of 10

gcc/ChangeLog:

	* gcov.cc (generate_results): Count branches, conditions.
	(function_summary): Output branch, calls, condition count.