Add SOVERSION to libobs-opengl

Because libobs-opengl is a public library, it's customary to have SONAME
embedded in the library file.  Also remove the prefix override and
remove the prefixing "lib" from the output name.  This also requires us
to pass the library file name to dlopen invocations.

CMakeLists.txt

@@ -72,7 +72,6 @@ endif()
 if(NOT INSTALLER_RUN)
 	add_subdirectory(deps)
 
-	add_subdirectory(libobs)
 
 	if(WIN32)
 		add_subdirectory(libobs-d3d11)
@@ -80,6 +79,7 @@ if(NOT INSTALLER_RUN)
 	endif()
 
 	add_subdirectory(libobs-opengl)
+	add_subdirectory(libobs)
 	add_subdirectory(obs)
 	add_subdirectory(plugins)
 	add_subdirectory(test)