ab/no-kwset, was Re: What's cooking in git.git (Jun 2019, #07; Fri, 28)

> * ab/no-kwset (2019-06-28) 9 commits
>  - grep: use PCRE v2 for optimized fixed-string search
>  - grep: remove the kwset optimization
>  - grep: drop support for \0 in --fixed-strings <pattern>
>  - grep: make the behavior for NUL-byte in patterns sane
>  - grep tests: move binary pattern tests into their own file
>  - grep tests: move "grep binary" alongside the rest
>  - grep: inline the return value of a function call used only once
>  - grep: don't use PCRE2?_UTF8 with "log --encoding=<non-utf8>"
>  - log tests: test regex backends in "--encode=<enc>" tests
>
>  Retire use of kwset library, which is an optimization for looking
>  for fixed strings, with use of pcre2 JIT.
>
>  Will merge to 'next'.