fixup??? grep: make PCRE2 aware of custom allocator

It is _not_ nedmalloc-specific! Never was, never will. As soon as you
use e.g. the LD_PRELOAD trick to use jemalloc, the very same issues will
arise as I reported earlier: a block that was allocated via PCRE2 wants
to be `free()`d via the custom allocator, which will cause serious
issues unless we make sure that PCRE2 uses the same allocator as Git.

Besides, the location where `pcre2_global_context` was initialized is
completely wrong. That code path was not even close to being hit in
t7816.48, however, that test case really needs that context.

Let's stop trying to be smart (and failing at it), and instead just
initialize the global context in `grep_init()` and be done with these
problems once and for all. The chase stopped being fun a month ago.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

grep.c

@@ -19,7 +19,6 @@ static struct grep_opt grep_defaults;
 #ifdef USE_LIBPCRE2
 static pcre2_general_context *pcre2_global_context;
 
-#ifdef USE_NED_ALLOCATOR
 static void *pcre2_malloc(PCRE2_SIZE size, MAYBE_UNUSED void *memory_data)
 {
 	return malloc(size);
@@ -30,7 +29,6 @@ static void pcre2_free(void *pointer, MAYBE_UNUSED void *memory_data)
 	return free(pointer);
 }
 #endif
-#endif
 
 static const char *color_grep_slots[] = {
 	[GREP_COLOR_CONTEXT]	    = "context",
@@ -176,6 +174,12 @@ void grep_init(struct grep_opt *opt, struct repository *repo, const char *prefix
 	struct grep_opt *def = &grep_defaults;
 	int i;
 
+#if defined(USE_LIBPCRE2)
+	if (!pcre2_global_context)
+		pcre2_global_context = pcre2_general_context_create(
+					pcre2_malloc, pcre2_free, NULL);
+#endif
+
 #ifdef USE_NED_ALLOCATOR
 #ifdef USE_LIBPCRE1
 	pcre_malloc = malloc;
@@ -343,11 +347,6 @@ void append_header_grep_pattern(struct grep_opt *opt,
 void append_grep_pattern(struct grep_opt *opt, const char *pat,
 			 const char *origin, int no, enum grep_pat_token t)
 {
-#if defined(USE_LIBPCRE2) && defined(USE_NED_ALLOCATOR)
-	if (!pcre2_global_context && opt->ignore_case && has_non_ascii(pat))
-		pcre2_global_context = pcre2_general_context_create(
-					pcre2_malloc, pcre2_free, NULL);
-#endif
 	append_grep_pat(opt, pat, strlen(pat), origin, no, t);
 }