hush: fix bkslash+newline handling and number validation in ${NN} and ${#NN}

Entering "${1a}" into interactive shell was making it exit.

function                                             old     new   delta
parse_dollar                                         824     958    +134
i_getch_and_eat_bkslash_nl                             -      44     +44
parse_expr                                           917     938     +21
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/0 up/down: 199/0)             Total: 199 bytes

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

1 files changed, 14 insertions, 0 deletions

diff --git a/shell/hush_test/hush-parsing/bkslash_newline4.tests b/shell/hush_test/hush-parsing/bkslash_newline4.tests
new file mode 100755
index 000000000..c8f5037c4
--- /dev/null
+++ b/shell/hush_test/hush-parsing/bkslash_newline4.tests
@@ -0,0 +1,14 @@
+set -- 1 22 333
+echo 1:$\
+1
+echo 22:$\
+{\
+2\
+}
+echo 3:$\
+{\
+#\
+3\
+}
+echo Ok:$\
+?