[perl #123711] Fix crash with 0-5x-l{0}

perl-5.8.0-117-g6f33ba7, which added the XTERMORDORDOR hack, did not
change the leftbracket code to treat XTERMORDORDOR the same way as
XTERM, so -l {0} and getc {0} (among other ops) were treating {...} as
a block, rather than an anonymous hash.  This was not, however, being
turned into a real block with enter/leave ops to protect the stack,
so the nextstate op was corrupting the stack and possibly freeing mor-
tals in use.

This commit makes the leftbracket code check for XTERMORDORDOR and
treat it like XTERM, so that -l {0} once more creates an anonymous
hash.  There is really no way to get to that hash, though, so all I
can test for is the crash.

t/base/lex.t

@@ -482,3 +482,6 @@ print "not " unless &{sub :lvalue { "a" }} eq "a";
 print "ok $test - &{sub :lvalue...}\n"; $test++;
 print "not " unless ref +(map{sub :lvalue { "a" }} 1)[0] eq "CODE";
 print "ok $test - map{sub :lvalue...}\n"; $test++;
+
+# Used to crash [perl #123711]
+0-5x-l{0};

toke.c

@@ -5506,6 +5506,7 @@ Perl_yylex(pTHX)
 	}
 	switch (PL_expect) {
 	case XTERM:
+	case XTERMORDORDOR:
 	    PL_lex_brackstack[PL_lex_brackets++] = XOPERATOR;
 	    PL_lex_allbrackets++;
 	    OPERATOR(HASHBRACK);