MacOS X/Darwin kernel supports a few tricky methods to access
a resource fork via ANSI C or POSIX interface. Current resource
fork accessor tries all possible methods to support all kernels.
But if a method could open a resource fork but no font is found,
there is no need to try other methods older than tested method.
To determine whether the rule index is for Darwin VFS, a local
function ftrfork.c::raccess_rule_by_darwin_vfs() is introduced.
To use this function in ftobjs.c etc but it should be inlined,
it is exposed by ftbase.h.
* src/base/ftrfork.c (FT_RFork_Rule): New enum type to identify
the rules to access the resource fork.
(raccess_guess_rec): New structure to bind the rule function and
rule enum type.
(FT_Raccess_Guess): The list of the rule functions is replaced by
(raccess_guess_table): This. This is exposed to be used by other
intra module functions.
(raccess_rule_by_darwin_vfs): A function to return a boolean
if the rule specified by the rule index is based on Darwin VFS.
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