Two leaks can happen: if idx is -1, the newly allocated entry may not be freed.
Also, for X509_PURPOSE_add, if only one BUF_strdup succeeds, it will leak.
Restructure both so that the allocations happen ahead of time and are properly
cleaned up. This avoids leaving an existing entry in a half-broken state.
Found (sort of) by scan-build; because of all the indirections and DYNAMIC
flags, it doesn't actually realize the leak's been fixed.
Change-Id: I5521889bd14e007b3f62b6a4906d7c346698b48c
Reviewed-on: https://boringssl-review.googlesource.com/2209
Reviewed-by: Adam Langley <agl@google.com>
Initial fork from f2d678e6e89b6508147086610e985d4e8416e867 (1.0.2 beta).
(This change contains substantial changes from the original and
effectively starts a new history.)
