Remove wxMGL port.

The company behind MGL toolkit (SciTech) doesn't exist since several years and
this port is not used by anybody, so remove it to ease maintenance burden.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70353 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/overviews/envvars.h

@@ -27,13 +27,5 @@ wxWidgets programs.
         @c /usr/local or @c /usr). You can set WXPREFIX if you are for example
         distributing a binary version of an application and you don't know in advance
         where it will be installed.}
-@itemdef{WXMODE,
-        (wxMGL only.)
-        Sets MGL video mode. The value must be in form
-        @e widthx@e height-@e depth. The default is @c 640x480-16.}
-@itemdef{WXSTDERR,
-        (wxMGL only.)
-        Redirects stderr output to a file.}
-
 */