New function: sm_print_r()

New function: sm_print_r()
This is intended to be a debugging function.  Ever wanted to do a print_r, but found that some of the values were "eaten" by your browser's parser because they had <> in them?  Use this function instead.  It runs htmlentities() on the output of print_r() AND as a bonus wraps the entire thing in <pre> and </pre> tags.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@5199 7612ce4b-ef26-0410-bec9-ea0150e637f0