syncqt: complain if a public header includes a private one

We should even cause syncqt to exit, but that would cause developers
trying to test something to be unable to. So leave it just with an
"ERROR" message. That is hopefully enough.

Change-Id: Ib056b47dde3341ef9a52ffff13ef5f8588b62b99
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

bin/syncqt.pl

@@ -1190,6 +1190,7 @@ if($check_includes) {
                                     }
                                     if ($include) {
                                         if ($public_header) {
+                                            print STDERR "$lib: ERROR: $iheader includes private header $include\n" if ($include =~ /_p.h$/);
                                             for my $trylib (keys(%modules)) {
                                                 if(-e "$out_basedir/include/$trylib/$include") {
                                                     print "$lib: WARNING: $iheader includes $include when it should include $trylib/$include\n";