package/swig: bump version to 3.0.7

This patch bumps the swig package to the current major release, the
comment about the CMake fix was also updated to reflect the version
bump. Swig 3.0.7 was positively tested using this defconfig:

BR2_TOOLCHAIN_BUILDROOT_INET_RPC=y
BR2_TOOLCHAIN_BUILDROOT_LOCALE=y
BR2_TOOLCHAIN_BUILDROOT_CXX=y
BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
BR2_PACKAGE_KODI=y
BR2_PACKAGE_KODI_LIBCEC=y
BR2_PACKAGE_TRACE_CMD=y
BR2_PACKAGE_MESA3D=y
BR2_PACKAGE_MESA3D_DRI_DRIVER_I965=y
BR2_PACKAGE_XORG7=y
BR2_PACKAGE_LIBFTDI1=y
BR2_PACKAGE_LIBFTDI1_PYTHON_BINDINGS=y
BR2_PACKAGE_LIBSEMANAGE=y
BR2_PACKAGE_GNURADIO=y

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