Deprecate all PackFile_* functions

[whiteknight]

Several functions in src/packfile/*.c are being marked with PARROT_EXPORT and they should not be. Many of these functions are internal-only routines and shouldn't be exposed directly.

All functions named "PackFile_*" should be deprecated. They are being replaced by a new set of API functions named "Parrot_pf_*", per conventions.

[cotto]

+1

[whiteknight]

Cotto gave the greenlight for this ticket. I'm going to add the notice to api.yaml. I'll be posting upgrade docs when we've got more of the new interface implemented.

[whiteknight]

I've cleaned up several API functions in the whiteknight/pbc_pbc branch, which recently merged to master. There are now properly-named replacements for most (not all) of the externally-used API functions from the packfile subsystem. I've included comments throughout src/packfile/api.c to indicate the intended upgrade paths for most of the remaining deprecated functions.

There are a few stragglers, like PackFile_fixup_subs which are not going to be replaced directly. I am still working to find replacements for these cases. They will probably tracked in other tickets.

[whiteknight]

We've done the lion's share of work on this ticket. All remaining instances of "PackFile_*" functions are not renamed because of larger issues which can be addressed in different tickets. I'm closing this one.