Make sure to escape backslashes and single quotes for buildinf.h

Reviewed-by: NRich Salz <rsalz@openssl.org>

util/mkbuildinf.pl

@@ -17,8 +17,9 @@ print <<"END_OUTPUT";
 END_OUTPUT
 my $ctr = 0;
 foreach my $c (split //, $cflags) {
+    $c =~ s|([\\'])|\\$1|;
     # Max 18 characters per line
-    if  (($ctr++ % 18) == 0) {
+    if  (($ctr++ % 16) == 0) {
         if ($ctr != 1) {
             print "\n";
         }