Merge branch 'ab/grep-pcre2-allocfix'

Updates to memory allocation code around the use of pcre2 library. * ab/grep-pcre2-allocfix: grep/pcre2: move definitions of pcre2_{malloc,free} grep/pcre2: move back to thread-only PCREv2 structures grep/pcre2: actually make pcre2 use custom allocator grep/pcre2: use pcre2_maketables_free() function grep/pcre2: use compile-time PCREv2 version test grep/pcre2: add GREP_PCRE2_DEBUG_MALLOC debug mode grep/pcre2: prepare to add debugging to pcre2_malloc() grep/pcre2: correct reference to grep_init() in comment grep/pcre2: drop needless assignment to NULL grep/pcre2: drop needless assignment + assert() on opt->pcre2