hush: support "break N" and "continue N"

hush: support "break N" and "continue N"
 fix non-detection of builtins and applets in "v=break; ...; $v; ..." case
 add testsuite entries for the above

function                                             old     new   delta
builtin_break                                         12      93     +81
run_list                                            1948    1971     +23
builtin_continue                                      12      21      +9
pseudo_exec_argv                                     132     138      +6
builtin_exec                                          23      25      +2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/0 up/down: 121/0)             Total: 121 bytes