package/libv4l: needs headers >= 3.0

package/libv4l: needs headers >= 3.0

libv4l includes linux/media.h, which was introduced in v.2.6.39.

So, require at least 3.0 to be sure, since we have toolchains (like the
Code Sourcery Powerpc 2011.03) that still use 2.6.38 headers.

Fixes:
    http://autobuild.buildroot.net/results/ff7/ff7977c1cea0edfd230e12b74fc2c34bac7a0e4e/
    http://autobuild.buildroot.net/results/2bd/2bd30d942ec718e0a46ba2d1c043c9b6e2e6578b/
    http://autobuild.buildroot.net/results/c37/c371f4de7ec4b959310ca8e08cf289385fa0feae/
    ...

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>