reset() for probe_avg_mag_sqrd
README files: Fix typos.
README: Fix incorrect URL.
volk: use literal shuffle parameters in avx 32fc_deinterleavers

Using anything put the literal value is a non-standard extension
that clang does not support.
Merge remote-tracking branch 'stefanolt/master'
Merge remote-tracking branch 'uwehermann/readme_fixes' into maint
Merge branch 'maint'