xbmc: Allow compilation with uClibc

- Add dependencies needed by xbmc on BR2_LARGEFILE, BR2_INET_IPV6 &
  BR2_USE_WCHAR after the removal of BR2_TOOLCHAIN_USES_GLIBC
- Add xbmc-0002-mathutil.patch to fix ARM compilation

[Thomas: factorize architecture dependency in a new
BR2_PACKAGE_XBMC_ARCH_SUPPORTS option.]

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>