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Merge pull request #1279 from cakebaker/patch-1

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Make named capture groups compatible with older PCRE versions.

CentOS is terrible and generally contains very old versions of PCRE.
Update patterns to use more backwards compatible named capture groups.

Fixes #3821
Add missing h() calls to exception stack traces.
Add missing html escaping.

This should have been here the whole time. Many of these variables could
contain user input.