Remove use of colon in decls for Checked C bounds and where clause declarations

[dtarditi]

We have introduced new keywords beginning with _ for the Checked C bounds annotations and where clauses, as part of creating erasable syntax. We no longer need the colon (:) to declare bounds declarations and where clauses from in declarations - there is not a potential for collisions.

We should update tests to remove the use of the ':' and to use the new keywords. We should update the syntax descriptions on the Wiki and in the spec to deprecate usage of the :. We'll remove support in the milestone after the v1.0 release (the 3C tools and various real-world codbases needs to be updated before deprecating compiler support).

[mwhicks1]

To elaborate on your last sentence, the repos are

• https://github.com/checkedc/checkedc-vsftpd
• https://github.com/checkedc/checkedc-tiny-bignum-c
• https://github.com/checkedc/checkedc-thttpd
• https://github.com/checkedc/checkedc-icecast
• https://github.com/checkedc/checkedc-libjpeg-tutorial