Give internal functions julia-- prefix

[non-Jedi]

At the next major version bump, we should rename all internal functions with julia- prefix to have a julia-- prefix. Here's the list I identified after a quick survey. Please reply if you believe any of these should be part of the packages public interface. Many of these should also be given a -p predicate suffix.

• julia-syntax-comment-or-string-p
• julia-in-comment
• julia-in-string
• julia-in-brackets
• julia-at-keyword
• julia-safe-backward-sexp
• julia-following-import-export-using
• julia-last-open-block-pos
• julia-last-open-block
• julia-paren-indent
• julia-prev-line-skip-blank-or-comment
• julia-indent-hanging
• julia-indent-in-string
• julia-indent-import-export-using
• julia-syntax-context-type
• julia-looking-at-beginning-of-defun
• julia-beginning-of-defun
• julia-end-of-defun
• julia-looking-at-beginning-of-defun

Cross-reference https://github.com/JuliaEditorSupport/julia-emacs/pull/115#discussion_r454986503

[tpapp]

Thanks for making this list, I agree with both the contents and adding -p where applicable.