If there is no pipe in the logger path, dont' assume
it's a process to fork, rather, assume it's a file.
Open the file in append mode and set up a signal handler
for log rotation.

Add log.rotate() function, doing the same as the signal handler,
useful when one uses a built-in logger.
The function does nothing if the logger is a pipe.

Fixes gh-225

Also fixes #264

Tarantool support three modes:

1. A script filename is passed to binary or server started using #!.
Tarantool read file contents and execute code as a whole chunk.
2. stdin is not a tty. Tarantool read stdin until EOF and execute
code as a whole chunk.
3. stdin is a tty. Tarantool starts in interactive mode and
processes console input line by line using dostring().

Please see the difference between #2 and #3.

This patch adds a new Lua module called 'pickle'. This module incorporates
former box.pack() and box.unpack() functions. These functions removed from
core because they are not needed for box anymore. This patch also removes all
box-specific formats from these functions.

(hat tip to Petr Yanovich).

A fix and a test case for gh-300: misleading error message for a
non-existing function.

First, check that a function exists. Then check access rights
to the function.

The confusion arose when trying to create a space with an
existing id.
The error message is no longer misleading.

Conflicts:
	src/lua/init.cc

* error(fmt, args)
* warn(fmt, args)
* info(fmt, args)
* debug(fmt, args)

All bultin modules can be loaded with require('modulename')
instead of require('box.modulename')

Other changes:

 * _G.box is not initialized from tarantool_lua_init() anymore
 * box.info, box.stat, box.snapshot moved to src/box/lua
 * box.coredump() => coredump()
 * box.xxx = require('box.xxx') removed from tests