bugfix: dgcov.pl shows wrong line numbers

dgcov.pl was putting gcov execution counters on wrong lines in the report (*.dgcov files were correct), because it was incrementing the new line number for diff lines starting from '-' (lines from the old file, not present in the new)

Author: vuvova

mysql-test/dgcov.pl

@@ -112,8 +112,7 @@ sub print_gcov_for_diff {
  $acc.=sprintf '%9s:%5s:%s', '', $lnum, $' if /^ /;
  ++$printme, $acc.=sprintf '%9s:%5s:%s', gcov_prefix($fcov->{$lnum}), $lnum, $' if /^\+/;
  die "$_^^^ dying", unless /^[- +]/;
- ++$lnum;
- --$cnt;
+ ++$lnum, --$cnt unless /^-/;
  }
  print $acc if $printme;
  close PIPE or die "command '$cmd' failed: $!: $?";