libidn2: new package

libidn2: new package

Libidn2 is an implementation of the IDNA2008 + TR46
specifications (RFC 5890, RFC 5891, RFC 5892, RFC 5893,
TR 46).

http://www.gnu.org/software/libidn/

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
[Thomas:
 - Use positive logic to test the BR2_PACKAGE_LIBIDN2_BINARY
   condition.
 - Put the definition of LIBIDN2_REMOVE_BINARY inside the
   BR2_PACKAGE_LIBIDN2_BINARY condition, as suggested by Arnout.
 - Adjust license details: library is under GPL-2.0+ or LGPL-3.0+,
   while the command line tool is under GPL-3.0+.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>