qt5script: correct license information

qt5script: correct license information

The license information in qt5script was just copied from all the other
qt5 modules, but it is different (and complicated).

- libQt5Script itself contains the third-party JavaScriptCore source.
  JavaScriptCore has a number of licenses: BSD-2-Clause, BSD-3-Clause,
  LGPL-2.0+, LGPL-2.1+. Since it is all linked together, the end
  result will be BSD-3-Clause and LGPL-2.1+.

  The different BSD licenses are all slightly different (different
  authors, which affects the third clause in particular). Only one
  separate license file is provided, so let's use that one.

  There is an LGPL-2.0 license file, which is slightly different from
  the top-level LICENSE.LGPLv21, so let's add that one as well.

- libQt5Script also contains Qt-specific code which is all licensed
  under LGPL-2.1 only. This is covered by the LICENSE.LGPLv21 file.
  It merges with the LGPL-2.1+ from JavaScriptCore but limits it to
  2.1 only.

- libQt5ScriptTools is a separate libary containing just the script
  debugger. It is covered by the usual Qt license:
  * LGPL-2.1 or LGPL-3.0 with exception for Qt 5.6;
  * LGPL-3.0 or GPL-2.0+ for Qt 5.9 (actually it is GPL-2.0 or GPL-3.0
    or any later version approved by the KDE Qt foundation, but let's
    keep it simple :-). Note that there is no LICENSE.GPLv2 provided,
    only LICENSE.GPLv3. Also, there is an LGPL_EXCEPTION.txt file but
    no mention of an exception anywhere in the sources.

Update the license information with all of the above. Also add hashes
for the new license files from JavaScriptCore.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>