hush: fix "$v" expansion in case patterns when v='[a]'

function                                             old     new   delta
run_list                                            1053    1063     +10
setup_redirects                                      311     320      +9
encode_then_expand_string                            135     142      +7
run_pipe                                            1784    1789      +5
expand_assignments                                    81      86      +5
expand_string_to_string                              124     125      +1
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(add/remove: 0/0 grow/shrink: 6/0 up/down: 37/0)               Total: 37 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/hush_test/hush-quoting/case_glob1.right b/shell/hush_test/hush-quoting/case_glob1.right
new file mode 100644
index 0000000..b478595
--- /dev/null
+++ b/shell/hush_test/hush-quoting/case_glob1.right
@@ -0,0 +1 @@
+s