Reflect secure coding policy in coding standard of only using Crypt::hashBase64() for hashes

Problem/Motivation

State what you believe is wrong or missing from the current standards.

Proposal:
mirror into the coding standards this standard of using only Drupal's hash helper functions when a hash is needed:

https://www.drupal.org/docs/7/security/writing-secure-code-0/use-of-hash...

The older functions are not significantly faster and offer less collision resistance, which is a key element of hash function quality. If there are (atypical and uncommon) cases where code actually needs a shorter hash string, it is better to truncate a sha-2 hash instead of using one of the deprecated functions:

http://crypto.stackexchange.com/questions/9435/is-truncating-a-sha512-ha...

compared to using sha-1, "truncating one of the SHA-2 functions to 160 bits is around 2^20 times stronger when it comes to collision resistance."

Note that 160 bits means taking 27 characters of the base64 encoded output. The absolute minimum substring length used should be 21 chars (126 bits) of base 64 output. Any use of a substring should be clearly justified in code comments.

Basically - it should be a coding standards violation and flagged automatically if people are using a different method to hash values.

related current core patch: #2569119: Use Crypt::hashBase64(), not hash('crc32b') or sha1 for placeholder tokens

Prior coding standard issue for Core that's too meandering: #2268875: [Policy, no patch] Using md5()/sha1()/crc32b in Drupal code

Benefits

If we adopted this change, the Drupal Project would benefit by ...

Three supporters required

1. https://www.drupal.org/u/{userid} (yyyy-mm-dd they added support)
2. https://www.drupal.org/u/{userid} (yyyy-mm-dd they added support)
3. https://www.drupal.org/u/{userid} (yyyy-mm-dd they added support)

Proposed changes

Provide all proposed changes to the Drupal Coding standards. Give a link to each section that will be changed, and show the current text and proposed text as in the following layout:

1. {link to the documentation heading that is to change}

Current text

Add current text in blockquotes

Proposed text

Add proposed text in blockquotes

2. Repeat the above for each page or sub-page that needs to be changed.

Remaining tasks

1. Create this issue in the Coding Standards queue, using the defined template
2. Add supporters
3. Create a Change Record
4. Review by the Coding Standards Committee
5. Coding Standards Committee takes action as required
6. Discussed by the Core Committer Committee, if it impacts Drupal Core
7. Final review by Coding Standards Committee
8. Documentation updates
   1. Edit all pages
   2. Publish change record
   3. Remove 'Needs documentation edits' tag
9. If applicable, create follow-up issues for PHPCS rules/sniffs changes

For a full explanation of these steps see the Coding Standards project page