math/wxmaxima: Make WxMaxima find its own documentation

Fix the resources directory, so that WxMaxima actually finds its own
documentation (if installed).

math/wxmaxima/Makefile

 PORTNAME=	wxmaxima
 PORTVERSION=	23.02.0
 DISTVERSIONPREFIX=	Version-
+PORTREVISION=	1
 CATEGORIES=	math
 
 MAINTAINER=	salvadore@FreeBSD.org

math/wxmaxima/files/patch-src_Dirstructure.cpp

+--- src/Dirstructure.cpp.orig	2023-02-19 14:20:34 UTC
++++ src/Dirstructure.cpp
+@@ -120,6 +120,7 @@ wxString Dirstructure::ResourcesDir() const {
+     exepath = exe.GetPath();
+   } else {
+     exepath = CMAKE_INSTALL_PREFIX;
++    exepath.Append("/share");
+   }
+   return exepath;
+ }