libobs/util: Add functions to inhibit sleep

These fucntions prevent the computer from going to sleep, hibernating,
or starting up a screen saver.

On linux, it will also attempt to use DBus to prevent gnome/kde/etc
sleep, but it's not necessarily required in order to compile the
library.  Otherwise, it will simply call "xdg-screensaver reset" once
every 30 seconds to reset the screensaver timer.

libobs/CMakeLists.txt

@@ -9,6 +9,12 @@ include_directories(${FFMPEG_INCLUDE_DIRS})
 
 list(REMOVE_ITEM FFMPEG_LIBRARIES ${FFMPEG_AVCODEC_LIBRARIES})
 
+if(UNIX)
+	find_package(DBus QUIET)
+else()
+	set(HAVE_DBUS "0")
+endif()
+
 find_package(ImageMagick QUIET COMPONENTS MagickCore)
 
 if(NOT ImageMagick_MagickCore_FOUND AND NOT FFMPEG_AVCODEC_FOUND)
@@ -103,6 +109,15 @@ elseif(UNIX)
 		util/pipe-posix.c
 		util/platform-nix.c)
 
+	if(DBUS_FOUND)
+		set(libobs_PLATFORM_SOURCES ${libobs_PLATFORM_SOURCES}
+			util/platform-nix-dbus.c)
+		include_directories(${DBUS_INCLUDE_DIRS})
+		set(libobs_PLATFORM_DEPS
+			${libobs_PLATFORM_DEPS}
+			${DBUS_LIBRARIES})
+	endif()
+
 	if(${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD")
 		# use the sysinfo compatibility library on bsd
 		find_package(Libsysinfo REQUIRED)