package/libglew: bump to version 2.1.0

See 2.1.0 Change Log:
http://glew.sourceforge.net/log.html



Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>