package/python-numpy: add reverse dependency on packages using python-numpy

package/python-numpy: add reverse dependency on packages using python-numpy

Since commit 1aa59097e61d524bb55ab1fcd4fbe5098b3e0bed[1] is merged, a
new build failure occurs when selecting packages which needs
python-numpy as dependency.

This fix a build issue[2] by adding the correct reverse dependencies
to the following packages :
- gnuradio (for python support)
- opencv3 (for python support)
- piglit
- python-matplotlib

So :
- adding to every listed packages
  `depends on !(BR2_TOOLCHAIN_USES_GLIBC || BR2_TOOLCHAIN_USES_MUSL)`
  and add a comment to explain what happend.

[1] https://git.buildroot.net/buildroot/commit/?id=1aa59097e61d524bb55ab1fcd4fbe5098b3e0bed
[2] http://autobuild.buildroot.org/results/b76/b76b6cf9602bcf5df69a7276762eab54cf74007b

Signed-off-by: Alexandre PAYEN <alexandre.payen@smile.fr>
Cc: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Damien DUVAL <damien.duval@smile.fr>
Cc: Romain Naour <romain.naour@smile.fr>
Reviewed-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>