hush: fix handling of \<eof> in double-quoted strings

function                                             old     new   delta
encode_string                                        268     250     -18

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/hush_test/hush-parsing/bkslash_eof2.tests b/shell/hush_test/hush-parsing/bkslash_eof2.tests
new file mode 100755
index 0000000..da1f08d
--- /dev/null
+++ b/shell/hush_test/hush-parsing/bkslash_eof2.tests
@@ -0,0 +1,4 @@
+printf 'echo "unterminated string\\' >test.tmp.sh
+. ./test.tmp.sh
+echo One:$?
+rm -f test.tmp.sh