Removed dependency on wxWidgets from Alien.

Updated source code to wxWidgets 3.1.1
Moved invocation of perl unit / integration tests to the xs project.

src/CMakeLists.txt

@@ -64,6 +64,9 @@ endif ()
 
 # Add the Slic3r GUI library, libcurl, OpenGL and GLU libraries.
 if (SLIC3R_GUI)
+    find_package(wxWidgets REQUIRED COMPONENTS base core adv html gl)
+    include(${wxWidgets_USE_FILE})
+
     target_link_libraries(slic3r libslic3r_gui ${wxWidgets_LIBRARIES} ${CURL_LIBRARIES})
 
     # Configure libcurl & OpenSSL