MINOR: initcall: record the file and line declaration of an INITCALL

MINOR: initcall: record the file and line declaration of an INITCALL

The INITCALL macros will now store the file and line number where they
are declared into the initcall struct, and RUN_INITCALLS() will assign
them to the global caller_file and caller_line variables, and will even
set caller_initcall to the current initall so that at any instant such
functions know where their caller declared them. This will help with
error messages and traces where a bit of context will be welcome.