Read from multiple apts files

[avidseeker]

Add the ability to read from multiple apts files. E.g: holidays.txt, school.txt, work.txt, apts.txt.

Currently:

$ calcurse -c apts.txt -c apts2.txt

Does not work.

[avidseeker]

Workaround in zsh:

$ calcurse -c =(cat "$XDG_DATA_HOME"/calcurse/apts*)

With the obvious drawback of losing changes on save. Note that bash process substitution calcurse -c <(cat apts*) does not work because calcurse seems to lseek the apts file.