Add VST Plugin

Closes jp9000/obs-studio#750

.gitmodules

@@ -1,7 +1,6 @@
 [submodule "plugins/win-dshow/libdshowcapture"]
 	path = plugins/win-dshow/libdshowcapture
 	url = https://github.com/jp9000/libdshowcapture.git
-
 [submodule "plugins/mac-syphon/syphon-framework"]
 	path = plugins/mac-syphon/syphon-framework
 	url = https://github.com/palana/Syphon-Framework.git
@@ -11,3 +10,6 @@
 [submodule "plugins/obs-browser"]
 	path = plugins/obs-browser
 	url = https://github.com/kc5nra/obs-browser.git
+[submodule "plugins/obs-vst"]
+	path = plugins/obs-vst
+	url = https://github.com/DDRBoxman/obs-vst.git

plugins/CMakeLists.txt

@@ -55,6 +55,12 @@ if(WIN32 OR APPLE)
 			message(STATUS "obs-browser submodule not found!  Please fetch submodules.  obs-browser plugin disabled.")
 		endif()
 	endif()
+
+	if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/obs-vst/CMakeLists.txt")
+		add_subdirectory(obs-vst)
+	else()
+		message(STATUS "obs-vst submodule not found!  Please fetch/update submodules.  obs-vst plugin disabled.")
+	endif()
 endif()
 
 add_subdirectory(image-source)