[PATCH v2 6/7] grep: un-break building with PCRE < 8.20

Amend my change earlier in this series ("grep: add support for the PCRE v1 JIT API", 2017-04-11) to un-break the build on PCRE v1 versions earlier than 8.20. The 8.20 release was the first release to have JIT & pcre_jit_stack in the headers, so a mock type needs to be provided for it on those

[PATCH v2 6/7] grep: un-break building with PCRE < 8.20

Amend my change earlier in this series ("grep: add support for the PCRE v1 JIT API", 2017-04-11) to un-break the build on PCRE v1 versions earlier than 8.20. The 8.20 release was the first release to have JIT & pcre_jit_stack in the headers, so a mock type needs to be provided for it on those