Description of problem:
Multiple buffer overflows leading to arbitrary code execution;
see https://bugs.exim.org/show_bug.cgi?id=1636

Version-Release number of selected component (if applicable):
pcre version 8.33 - 8.37

How reproducible:
Always

Steps to Reproduce:
1. Start 'pcretest' from pcre-tools
2. Run this regex: /^(?P=B)((?P=B)(?J:(?P<B>c)(?P<B>a(?P=B)))>WGXCREDITS)/
   in the 're>' prompt

Actual results:
*** Error in `pcretest': free(): invalid next size (normal): 0x0000000001e8aa40 ***
*** Error in `pcretest': malloc(): memory corruption: 0x0000000001e8aae0 ***


Expected results:
 data>