Simplify error creating functions
Simplify error creating functions

Remove custom cfstring_constant macro in favour of CoreFoundations CFSTR

Remove cfstring_with_format as it was hard to use without leaking the
string

Add cferror_with_format which will create a custom description with the
given parameters

JaySandhu/vimdown,JaySandhu/vimdown,JaySandhu/vimdown