Unit tests must be done at integration process.

* Remove --enable-unittests and --disable-unittests and add --do-unittests function
* --do-unittests function will exit 0 on success.
* minetest and minetestserver binaries are launched with --do-unittests in travis build.

src/CMakeLists.txt

@@ -355,6 +355,10 @@ add_subdirectory(jthread)
 add_subdirectory(script)
 add_subdirectory(util)
 
+set (unittests_SRCS
+	test.cpp
+)
+
 set(common_SRCS
 	ban.cpp
 	base64.cpp
@@ -422,7 +426,6 @@ set(common_SRCS
 	sound.cpp
 	staticobject.cpp
 	subgame.cpp
-	test.cpp
 	tool.cpp
 	treegen.cpp
 	version.cpp
@@ -435,6 +438,7 @@ set(common_SRCS
 	${JTHREAD_SRCS}
 	${common_SCRIPT_SRCS}
 	${UTIL_SRCS}
+	${unittests_SRCS}
 )
 
 # This gives us the icon and file version information