examples: Add CMake glue to optionally build examples, as we do for the tests.

In fact, most of the CMake code was stolen from the test directory.

CMakeLists.txt

@@ -354,6 +354,9 @@ dep_option(SDL_INSTALL_TESTS   "Install test-cases" OFF "NOT SDL_DISABLE_INSTALL
 dep_option(SDL_TESTS_LINK_SHARED "link tests to shared SDL library" "${SDL_SHARED}" "SDL_SHARED;SDL_STATIC" "${SDL_SHARED}")
 set(SDL_TESTS_TIMEOUT_MULTIPLIER "1" CACHE STRING "Timeout multiplier to account for really slow machines")
 
+set_option(SDL_EXAMPLES           "Build the examples directory")
+dep_option(SDL_EXAMPLES_LINK_SHARED "link examples to shared SDL library" "${SDL_SHARED}" "SDL_SHARED;SDL_STATIC" "${SDL_SHARED}")
+
 if(VITA)
   set_option(VIDEO_VITA_PIB  "Build with PSVita piglet gles2 support" OFF)
   set_option(VIDEO_VITA_PVR  "Build with PSVita PVR gles/gles2 support" OFF)
@@ -3622,6 +3625,13 @@ if(SDL_TESTS)
   add_subdirectory(test)
 endif()
 
+##### Examples subproject (must appear after the install/uninstall targets) #####
+
+if(SDL_EXAMPLES)
+  set(HAVE_EXAMPLES ON)
+  add_subdirectory(examples)
+endif()
+
 ##### Fix Objective C builds #####
 string(APPEND CMAKE_OBJC_FLAGS " ${CMAKE_C_FLAGS}")