CMake cleanup

Several cleanups to the buildsystem:
 - Do better factoring of common libs between platforms.
 - Add support to building on Windows.
 - Remove Qt4 support.
 - Re-sort file lists and add missing headers.

externals/qhexedit/CMakeLists.txt

@@ -5,14 +5,17 @@ set(SRCS
             commands.cpp
             qhexedit.cpp
             qhexedit_p.cpp
-            xbytearray.cpp)
+            xbytearray.cpp
+            )
 
 set(HEADERS
+            commands.h
             qhexedit.h
-            qhexedit_p.h)
+            qhexedit_p.h
+            xbytearray.h
+            )
+
+create_directory_groups(${SRCS} ${HEADERS})
 
 add_library(qhexedit STATIC ${SRCS} ${HEADERS})
-if(USE_QT5)
-    target_link_libraries(qhexedit Qt5::Core Qt5::Widgets)
-endif()
-
+target_link_libraries(qhexedit ${CITRA_QT_LIBS})