Add support for reading PKCS#7 data from PEM files.

(There are times when I actually miss C++ templates.)

Change-Id: I3db56e4946ae4fb919105fa33e2cfce3c7542d37
Reviewed-on: https://boringssl-review.googlesource.com/3700
Reviewed-by: Adam Langley <agl@google.com>
3 files changed