Config file creation fails if XDG_CONFIG_HOME does not exist

[sparr]

#40 put the config file in XDG_CONFIG_HOME, which is ~/.config by default on most Linux systems. If that directory does not exist, then the following code will fail to create the config file and throw an error:

https://github.com/Jeija/gtkterm/blob/b5d27d92a3c7a64afd9cf7a438ee50cabfcafa9e/src/parsecfg.c#L168-L173

[wvdakker]

Will fix it in 2.x