Merge branch 'nd/icase' into maint

"git grep -i" has been taught to fold case in non-ascii locales correctly. * nd/icase: grep.c: reuse "icase" variable diffcore-pickaxe: support case insensitive match on non-ascii diffcore-pickaxe: Add regcomp_or_die() grep/pcre: support utf-8 gettext: add is_utf8_locale() grep/pcre: prepare locale-dependent tables for icase matching grep: rewrite an if/else condition to avoid duplicate expression grep/icase: avoid kwsset when -F is specified grep/icase: avoid kwsset on literal non-ascii strings test-regex: expose full regcomp() to the command line test-regex: isolate the bug test code grep: break down an "if" stmt in preparation for next changes