-- First of all style changes:

Most of the source files are close to edk2 style (no tabs, indent with two spaces, ...).

All commented out code uncommented and excluded from compilation with #if 0...#endif
(that allows to reformat all source with indenting tools).

All variables declarations moved to top of functions or blocks.

Some copy/paste abuse reduction.

-- Next compiler hickups:

Explicit type casts for assignments.

No more implicit support library calls for 64 bit datum manipulation.

-- Individual files:

Library/BdsDxe/GenericBds/macosx/device_inject.c -- set_usb_props() && was used were & should be (fake_vid).
Need to be split?

Library/BdsDxe/GenericBds/macosx/plist.c -- ParseTagInteger() uniry minus applied to unsigned int
produce did not make negative integer. Fixed. EFI_STATUS ParseTagDate() returned length instead of EFI_STATUS. Fixed.

Library/BdsDxe/GenericBds/macosx/smbios.c -- UpdateSmbiosString() strange code marked with #if 1...#endif.

Library/BdsDxe/GenericBds/macosx/Utils.c -- BOOLEAN hex2bin() returned (-2). Fixed to return FALSE.