Unable to compile Gelide on Ubuntu 18.04 LTS

[N0rbert]

Other user and I have installed Ubuntu 18.04 LTS amd64.
We are trying to compile Gelid on it.

But there is a problem with some functions from glibmm-2.4. You can see complete steps to reproduce on the aforementioned AskUbuntu link. The error message is below:

config.cpp: In constructor ‘CConfig::CConfig()’:
config.cpp:31:16: error: ‘build_filename’ is not a member of ‘Glib’
  l_cfg = Glib::build_filename(utils::getGelideDir(), GELIDE_CFG_FILE);
                ^~~~~~~~~~~~~~
config.cpp:33:11: error: ‘file_test’ is not a member of ‘Glib’
  if(Glib::file_test(l_cfg, Glib::FILE_TEST_EXISTS))
           ^~~~~~~~~
config.cpp:33:34: error: ‘FILE_TEST_EXISTS’ is not a member of ‘Glib’
  if(Glib::file_test(l_cfg, Glib::FILE_TEST_EXISTS))
                                  ^~~~~~~~~~~~~~~~
config.cpp: In destructor ‘virtual CConfig::~CConfig()’:
config.cpp:40:13: error: ‘build_filename’ is not a member of ‘Glib’
  save(Glib::build_filename(utils::getGelideDir(), GELIDE_CFG_FILE));
             ^~~~~~~~~~~~~~
Makefile:612: recipe for target 'config.o' failed
make[2]: *** [config.o] Error 1
make[2]: Leaving directory '/home/mate/Downloads/Gelide/src'
Makefile:553: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/home/mate/Downloads/Gelide'
Makefile:464: recipe for target 'all' failed
make: *** [all] Error 2

Could you please rewrite you code replacing obsolete GlibMM functions and constants such as

• build_filename from /usr/include/glibmm-2.4/glibmm/miscutils.h
• file_test, FILE_TEST_EXISTS from /usr/include/glibmm-2.4/glibmm/fileutils.h

Please note, your application compiles and works great on Ubuntu 16.04 LTS, but not on 18.04 LTS.