hush: finish and enable optional case...esac support. Code size cost:

function                                             old     new   delta
run_list                                            1891    2075    +184
parse_stream                                        1764    1847     +83
expand_strvec_to_string                                -      83     +83
done_word                                            647     715     +68
static.reserved_list                                 144     168     +24
static.reserved_match                                  -      12     +12
done_pipe                                             95     105     +10
builtin_exit                                          48      46      -2
builtin_eval                                         127      54     -73
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 5/2 up/down: 464/-75)           Total: 389 bytes

shell/hush_test/hush-misc/case1.right

@@ -0,0 +1,13 @@
+OK_1
+OK_21
+OK_22
+OK_23
+OK_31
+OK_32
+OK_41
+OK_42
+OK_43
+OK_44
+OK_51
+OK_52
+OK_53

shell/hush_test/hush-misc/case1.tests

@@ -0,0 +1,17 @@
+case w in a) echo SKIP;; w) echo OK_1;; w) echo WRONG;; esac
+
+t=w
+case $t in a) echo SKIP;; w) echo OK_21;; w) echo WRONG;; esac;
+case "$t" in a) echo SKIP;; w) echo OK_22;; w) echo WRONG;; esac;
+case w in a) echo SKIP;; $t) echo OK_23;; "$t") echo WRONG;; esac;
+
+case '' in a) echo SKIP;; w) echo WRONG;; *) echo OK_31;; esac;
+case '' in a) echo SKIP;; '') echo OK_32;; *) echo WRONG;; esac;
+
+case `echo w` in a) echo SKIP;; w) echo OK_41;; w) echo WRONG;; esac;
+case "`echo w`" in a) echo SKIP;; w) echo OK_42;; w) echo WRONG;; esac;
+case `echo w w` in a) echo SKIP;; w) echo WRONG;; 'w w') echo OK_43;; esac;
+case `echo w w` in a) echo SKIP;; w) echo WRONG;; w*) echo OK_44;; esac;
+
+case w in `echo w`) echo OK_51;; `echo WRONG >&2`w) echo WRONG;; esac;
+case w in `echo OK_52 >&2`) echo SKIP;; `echo`w) echo OK_53;; esac;