Add a specific error message for PCRE conflicts

When a different PCRE library is loaded than that which the stdlib
was compiled against, the compiled regular expressions may fail.
This compares the version strings of the compiled and loaded libpcre
and if different aborts (similar to how Julia will abort with BLAS error)
Merge pull request #4959 from mbauman/pcre_error_message

Add a specific error message for PCRE conflicts