bc: remove redundant JUMP generation when parsing 'while'

function                                             old     new   delta
zbc_parse_stmt_possibly_auto                        2065    2025     -40
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-40)             Total: -40 bytes
   text	   data	    bss	    dec	    hex	filename
 982035	    485	   7296	 989816	  f1a78	busybox_old
 981995	    485	   7296	 989776	  f1a50	busybox_unstripped

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

testsuite/bc.tests

@@ -107,6 +107,33 @@ if(1) {
 99
 "
 
+testing "bc continue in if" \
+	"bc" \
+	"\
+11
+21
+11
+31
+99
+" \
+	"" "\
+i=2
+while(i--) {
+        11
+        if(i) {
+                21
+                continue
+                22
+        } else {
+                31
+                continue
+                32
+	}
+        12
+}
+99
+"
+
 tar xJf bc_large.tar.xz
 
 for f in bc*.bc; do