Add support for SDL2 (#3732)

src/CMakeLists.txt

@@ -59,7 +59,9 @@ INCLUDE_DIRECTORIES(
 	${SNDIO_INCLUDE_DIRS}
 )
 
-IF(NOT ("${SDL_INCLUDE_DIR}" STREQUAL ""))
+IF(NOT ("${SDL2_INCLUDE_DIR}" STREQUAL ""))
+	INCLUDE_DIRECTORIES("${SDL2_INCLUDE_DIR}")
+ELSEIF(NOT ("${SDL_INCLUDE_DIR}" STREQUAL ""))
 	INCLUDE_DIRECTORIES("${SDL_INCLUDE_DIR}")
 ENDIF()
 
@@ -134,6 +136,7 @@ SET(LMMS_REQUIRED_LIBS
 	${QT_LIBRARIES}
 	${ASOUND_LIBRARY}
 	${SDL_LIBRARY}
+	${SDL2_LIBRARY}
 	${PORTAUDIO_LIBRARIES}
 	${SOUNDIO_LIBRARY}
 	${SNDIO_LIBRARY}

src/lmmsconfig.h.in

@@ -19,6 +19,7 @@
 #cmakedefine LMMS_HAVE_SOUNDIO
 #cmakedefine LMMS_HAVE_PULSEAUDIO
 #cmakedefine LMMS_HAVE_SDL
+#cmakedefine LMMS_HAVE_SDL2
 #cmakedefine LMMS_HAVE_STK
 #cmakedefine LMMS_HAVE_VST