changed quote-mark style in args passed to shell for *_install.pl so …

…that it works with cmd.exe and nmake.exe

Makefile.PL

@@ -322,7 +322,7 @@ sub MY::install {
 sub MY::postamble {
   my $paths;
   for my $key (keys %OPTIONS) {
-    $paths .= qq('$key=$OPTIONS{$key}' ) if defined $OPTIONS{$key};
+    $paths .= qq("$key=$OPTIONS{$key}" ) if defined $OPTIONS{$key};
   }
 qq{
 conf_install ::