bc: store only index in p->exits, it's the only thing used there

function                                             old     new   delta
zbc_parse_stmt_possibly_auto                        1967    1964      -3
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-3)               Total: -3 bytes
   text	   data	    bss	    dec	    hex	filename
 981937	    485	   7296	 989718	  f1a16	busybox_old
 981934	    485	   7296	 989715	  f1a13	busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

testsuite/bc.tests

@@ -134,6 +134,23 @@ while(i--) {
 99
 "
 
+testing "bc continue in for" \
+	"bc" \
+	"\
+1
+77
+2
+99
+" \
+	"" "\
+for(i=1; i<3; i++) {
+    i
+    if(i==2) continue
+    77
+}
+99
+"
+
 tar xJf bc_large.tar.xz
 
 for f in bc*.bc; do