Stop unterminated here-docs from leaking memory

MANIFEST

@@ -5370,6 +5370,7 @@ t/op/sub_lval.t			See if lvalue subroutines work
 t/op/substr.t			See if substr works
 t/op/substr_thr.t		See if substr works in another thread
 t/op/sub.t			See if subroutines work
+t/op/svleak.pl			Test file for svleak.t
 t/op/svleak.t			See if stuff leaks SVs
 t/op/switch.t			See if switches (given/when) work
 t/op/symbolcache.t		See if undef/delete works on stashes with functions

t/op/svleak.pl

@@ -0,0 +1 @@
+<<END

t/op/svleak.t

@@ -15,7 +15,7 @@ BEGIN {
 
 use Config;
 
-plan tests => 22;
+plan tests => 25;
 
 # run some code N times. If the number of SVs at the end of loop N is
 # greater than (N-1)*delta at the end of loop 1, we've got a leak
@@ -172,3 +172,12 @@ SKIP: {
     leak(2, 0, sub { eval q{ my $x = "x"; "abc" =~ /$x/ for 1..5 } }, '#114356');
 }
 
+SKIP: {
+    skip "disabled under -Dmad (eval leaks)" if $Config{mad};
+    leak(2, 0, sub { eval '"${<<END}"
+                 ' }, 'unterminated here-doc in quotes in multiline eval');
+    leak(2, 0, sub { eval '"${<<END
+               }"' }, 'unterminated here-doc in multiline quotes in eval');
+    leak(2, 0, sub { eval { do './op/svleak.pl' } },
+        'unterminated here-doc in file');
+}

toke.c

@@ -9681,6 +9681,8 @@ S_scan_heredoc(pTHX_ register char *s)
 		++PL_parser->herelines;
 	}
 	if (s >= bufend) {
+	    SvREFCNT_dec(herewas);
+	    SvREFCNT_dec(tmpstr);
 	    CopLINE_set(PL_curcop, (line_t)PL_multi_start);
 	    missingterm(PL_tokenbuf + 1);
 	}
@@ -9705,6 +9707,8 @@ S_scan_heredoc(pTHX_ register char *s)
 		++PL_parser->herelines;
 	}
 	if (s >= PL_bufend) {
+	    SvREFCNT_dec(herewas);
+	    SvREFCNT_dec(tmpstr);
 	    CopLINE_set(PL_curcop, (line_t)PL_multi_start);
 	    missingterm(PL_tokenbuf + 1);
 	}
@@ -9759,6 +9763,8 @@ S_scan_heredoc(pTHX_ register char *s)
 	CopLINE_set(PL_curcop, PL_multi_start + PL_parser->herelines + 1);
 	if (!lex_next_chunk(LEX_NO_TERM)
 	 && (!SvCUR(tmpstr) || SvEND(tmpstr)[-1] != '\n')) {
+	    SvREFCNT_dec(herewas);
+	    SvREFCNT_dec(tmpstr);
 	    CopLINE_set(PL_curcop, (line_t)PL_multi_start);
 	    missingterm(PL_tokenbuf + 1);
 	}