crypto: Split up crypto.c into multiple files

[hogand]

This is phase one of revamping crypto.c by splitting it up into many files. I tried to make as few changes as possible other than moving things around.

The order of the functions in each new C file is the same as in crypto.c so it's easier to verify that I didn't accidentally change anything. I used meld to double check each file against master crypto.c.

There should be no change in functionality with this PR. crypto_SUITE passes with OpenSSL 1.1.1a.

[CLAassistant]

All committers have signed the CLA.

[HansN]

Thanks for the PR!
Looks good so far. I've run the crypto and ssh tests with openssl 0.9.8 and 1.0.1 without errors. Half of our nightly tests have now finnished and there was no crypto related error.
I have a comment on four lines in evp_compat.h which I will do in the code.

[sverker]

Looks good over all.

To reap further benefit of this modularization, you could move the calls to enif_open_resource_type into *_initialize functions within the corresponding .c file. That would make the resource types and their destructor functions internal to each .c file without the need to be exposed in the .h files.

[hogand]

I noticed in the existing code that if FIPS mode is enabled but runs into a problem in initialize() (fails to load or not passed a boolean), it returns 0 which indicates success. It seems like that should return __LINE__ like the rest of the function to indicate failure.

In this PR, since init_atoms() has that FIPS init procedure, initialize() will return __LINE__ when FIPS init fails. That is a change in behavior compared to master, but it seems like a bug fix. I was keeping the same behavior as master until that last commit.

[HansN]

Thank you very much for the PR. More are welcome!