Unexport EC_GROUP_copy.

EC_GROUP_copy is an rather unfriendly function; it doesn't work if the groups
have different[*] underlying EC_METHODs, but this notion is not exposed through
the API. I found no callers of EC_GROUP_copy in external code.

This leaves the precompute_mult functions as the remaining mutable API exposed
through EC_GROUP.

[*] Though, of the two EC_METHODs right now, simple.c is entirely unused.

Change-Id: Iabb52518005250fb970e12b3b0ea78b4f6eff4a0
Reviewed-on: https://boringssl-review.googlesource.com/3631
Reviewed-by: Adam Langley <agl@google.com>
3 files changed