Rename DSP::V1_0::native to DSP::V3_0::native

Rename DSP::V1_0::native to DSP::V3_0::native

* scripts/Dpkg/Source/Package/V1_0/native.pm: This file got
renamed into...
* scripts/Dpkg/Source/Package/V3_0/native.pm: The goal is to
not pollute the namespace of versions 1.0 and 2.0. The usage
of the format specifier between parenthesis is thus limited
to version 3.0.
* scripts/dpkg-source.pl: Updated to take into account the
previous renaming.
* scripts/Dpkg/Source/Package/V1_0.pm: Adapt to the name change
and two small bug fixes that affect building of native packages.
* scripts/Makefile.am, scripts/po/POTFILES.in: Register the new
file and remove the old one.