Remove meth_num in ex_data_impl.c.

It's unnecessary and Windows was unhappy about the signed/unsigned
comparisons.

Change-Id: If2c4a20de48a2cddb0a4e0ca01e84eef91b155db
Reviewed-on: https://boringssl-review.googlesource.com/1863
Reviewed-by: Adam Langley <agl@google.com>
1 file changed