Handle /[#]/ and /[(?#]/ with code blocks

This is a regression in 5.18.0.

In something like /[#](?{})/x, the perl toker incorrectly sees the '#' as a
comment and skips the code block without parsing it.

t/re/re_tests

@@ -1764,3 +1764,15 @@ A+?(*PRUNE)BC(?{})	AAABC	y	$&	ABC
 A+(*THEN)BC(?{})	AAABC	y	$&	AAABC
 A+(*PRUNE)BC(?{})	AAABC	y	$&	AAABC
 # vim: softtabstop=0 noexpandtab
+/[#]/	a#b	y	$&	#
+/[#]b/	a#b	y	$&	#b
+/[#]/x	a#b	y	$&	#
+/[#]b/x	a#b	y	$&	#b
+/[#](?{})/x	a#b	y	$&	#
+/[#](??{'b'})/x	a#b	y	$&	#b
+/(?#)(?{})b/	a#b	y	$&	b
+/(?#)(??{'b'})/	a#b	y	$&	b
+/[(?#](?{})b/	a#b	y	$&	#b
+/[(?#](??{'b'})/	a#b	y	$&	#b
+/(?#)(?{})b/x	a#b	y	$&	b
+/(?#)(??{'b'})/x	a#b	y	$&	b

toke.c

@@ -3285,12 +3285,12 @@ S_scan_const(pTHX_ char *start)
 	 * char, which will be done separately.
 	 * Stop on (?{..}) and friends */
 
-	else if (*s == '(' && PL_lex_inpat && s[1] == '?') {
+	else if (*s == '(' && PL_lex_inpat && s[1] == '?' && !in_charclass) {
 	    if (s[2] == '#') {
 		while (s+1 < send && *s != ')')
 		    *d++ = NATIVE_TO_NEED(has_utf8,*s++);
 	    }
-	    else if (!PL_lex_casemods && !in_charclass &&
+	    else if (!PL_lex_casemods &&
 		     (    s[2] == '{' /* This should match regcomp.c */
 		      || (s[2] == '?' && s[3] == '{')))
 	    {
@@ -3299,7 +3299,7 @@ S_scan_const(pTHX_ char *start)
 	}
 
 	/* likewise skip #-initiated comments in //x patterns */
-	else if (*s == '#' && PL_lex_inpat &&
+	else if (*s == '#' && PL_lex_inpat && !in_charclass &&
 	  ((PMOP*)PL_lex_inpat)->op_pmflags & RXf_PMf_EXTENDED) {
 	    while (s+1 < send && *s != '\n')
 		*d++ = NATIVE_TO_NEED(has_utf8,*s++);