wxmac: add option to build with STL classes

Closes Homebrew/homebrew#36769.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Formula/wxmac.rb

@@ -16,6 +16,8 @@ class Wxmac < Formula
   depends_on "libpng"
   depends_on "libtiff"
 
+  option "with-stl", "use standard C++ classes for everything"
+
   # Various fixes related to Yosemite. Revisit in next stable release.
   # Please keep an eye on http://trac.wxwidgets.org/ticket/16329 as well
   # Theoretically the above linked patch should still be needed, but it isn't. Try to find out why.
@@ -67,6 +69,8 @@ class Wxmac < Formula
       "--disable-monolithic"
     ]
 
+    args << "--enable-stl" if build.with? "stl"
+
     system "./configure", *args
     system "make", "install"
   end