Catch last space in regex in expose_stan_functions

[sbfnk]

Summary:

Fixes #1114 by catching the last space in the regex for expose_stan_functions, which can be a line break.
Previous PRs #1094 and #1099 did not completely fix this problem. Scanning the culpable line this should be the last one to fix.

Intended Effect:

Example in Issue #1114 works.

How to Verify:

Text example in Issue #1114

Side Effects:

None

Documentation:

n/a

Reviewer Suggestions:

@andrjohns (sorry, once more)

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company): Sebastian funk

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: GPLv3 (https://opensource.org/licenses/GPL-3.0)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[andrjohns]

LGTM, thanks