This got reset at some point, but not the files generated from it.
obj_mac.num is an input/output parameter to objects.pl and used to keep the
NIDs stable.

Imported from f2d678e6e89b6508147086610e985d4e8416e867, the point at which we
forked.

Change-Id: Ifd52b1aaa55054d37bc1217f2375a93302839e23
Reviewed-on: https://boringssl-review.googlesource.com/2472
Reviewed-by: Adam Langley <agl@google.com>

Initial fork from f2d678e6e8 (1.0.2 beta).

(This change contains substantial changes from the original and
effectively starts a new history.)