grep: fix -Fc regression

[mknos]

• Combining -F and -c flags had the incorrect result of showing matching lines followed by a count
• When debugging this I discovered the opt hash was supposed to be massaged so s-flag is set if c-flag is set

%perl grep -Fc '/' aa.c     # before patch
	/* I SHOULD BE INVISIBLE */
1

[itsnicksia]

This fixes an issue triggered on line 400 where line is still printed because only opt s is checked:

$opt->{'s'} || print $Mult && "$name:",
				$opt->{n} ? "$.:" : "", $_,
				( $opt->{p} || $opt->{P} ) && ( '-' x 20 ) . "\n";

[briandfoy]

changes: set -s implicitly when -c is used