Add PNG and wxWidgets 3.1.3 uniformly to all platforms with cmake build.

wx is built with png as a dependency, wxpng is disabled.

deps/EXPAT/EXPAT.cmake

@@ -0,0 +1,9 @@
+prusaslicer_add_cmake_project(EXPAT
+  # GIT_REPOSITORY https://github.com/nigels-com/glew.git
+  # GIT_TAG 3a8eff7 # 2.1.0
+  SOURCE_DIR          ${CMAKE_CURRENT_LIST_DIR}/expat
+)
+
+if (MSVC)
+    add_debug_dep(dep_EXPAT)
+endif ()