config.c: plumb the_reader through callbacks
The remaining references to "cf_global" are in config callback
functions. Remove them by plumbing "struct config_reader" via the
"*data" arg.
In both of the callbacks here, we are only reading from
"reader->source". So in the long run, if we had a way to expose readonly
information from "reader->source" (probably in the form of "struct
key_value_info"), we could undo this patch (i.e. remove "struct
config_reader" fom "*data").
Signed-off-by: Glen Choo <chooglen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>