Add multipul patterns function tio.expects() to Lua API

Add tio.expects() which has a table of patterns in the arguments to
support "OR" pattern waiting.

The return values of tio.expects() are:
1st: index of the matched pattern in the table. nil if unmatched.
2nd: a table of captures if one of the patterns are matched.
     nil if any of the patterns are unmatched and timeout.
3rd: all received strings in tio.expects() to treat the strings after
     match.

Add all received string to tio.expect()'s return values too.

For example,
  idx, captures, all_received = tio.expects( {"\nOK", "\nERROR"}, 1000 )
  captures, all_received = tio.expect( "\nPROMPT>", 1000 )

src/script.c

@@ -60,13 +60,31 @@ static char script_init[] =
 "    local str = ''\n"
 "    while true do\n"
 "        local c = tio.read(1, timeout)\n"
-"        if c then\n"
+"        if c == nil then\n"
+"            return nil, str\n"
+"        end\n"
 "        str = str .. c\n"
 "        if string.match(str, pattern) then\n"
-"                return string.match(str, pattern)\n"
+"            return string.match(str, pattern), str\n"
+"        end\n"
+"    end\n"
+"end\n"
+"tio.expects = function(patterns, timeout)\n"
+"    local str = ''\n"
+"    if type(patterns) ~= 'table' then\n"
+"        patterns = { patterns }\n"
+"    end\n"
+"    while true do\n"
+"        local c = tio.read(1, timeout)\n"
+"        if c == nil then\n"
+"            return nil, nil, str\n"
+"        end\n"
+"        str = str .. c\n"
+"        for idx, pat in ipairs(patterns) do\n"
+"            local captured = { string.match(str, pat) }\n"
+"            if #captured > 0 then\n"
+"                return idx, captured, str\n"
 "            end\n"
-"        else\n"
-"            return nil, str\n"
 "        end\n"
 "    end\n"
 "end\n"