Clean up and tweak build system

* Combine client and server man pages.
  * Update unit test options and available databases in man page.
  * Add `--worldname` to man page.
  * Fix a bunch of places where `"Minetest"` was used directly instead of `PROJECT_NAME`.
  * Disable server build by default on all operating systems.
  * Make `ENABLE_FREETYPE` not fail if FreeType isn't found.
  * Enable LevelDB, Redis, and FreeType detection by default.
  * Remove the `VERSION_PATCH_ORIG` hack.
  * Add option to search for and use system JSONCPP.
  * Remove broken LuaJIT version detection.
  * Rename `DISABLE_LUAJIT` to `ENABLE_LUAJIT`.
  * Rename `minetest_*` variables in `version.{h,cpp}` to `g_*`.
  * Clean up style of CMake files.

src/guiEngine.cpp

@@ -171,8 +171,8 @@ GUIEngine::GUIEngine(	irr::IrrlichtDevice* dev,
 		m_sound_manager = &dummySoundManager;
 
 	//create topleft header
-	std::wstring t = narrow_to_wide(std::string("Minetest ") +
-			minetest_version_hash);
+	std::wstring t = narrow_to_wide(std::string(PROJECT_NAME " ") +
+			g_version_hash);
 
 	core::rect<s32> rect(0, 0, g_fontengine->getTextWidth(t), g_fontengine->getTextHeight());
 	rect += v2s32(4, 0);
@@ -571,8 +571,8 @@ bool GUIEngine::downloadFile(std::string url, std::string target)
 /******************************************************************************/
 void GUIEngine::setTopleftText(std::string append)
 {
-	std::wstring toset = narrow_to_wide( std::string("Minetest ") +
-			minetest_version_hash);
+	std::wstring toset = narrow_to_wide(std::string(PROJECT_NAME " ") +
+			g_version_hash);
 
 	if (append != "")
 	{