[robots/nao-robot] Add missing deps on ros-xacro and ros-robot-state-publisher
[pkgtools/pkgin] Fix the definition of the path to "uname"

After commit:eca4e45, UNAME is only temporarily defined by robotpkg to locate
the preferences files, and it is not available to a package Makefile. Fix pkgin
by falling back to just "uname" if ${UNAME} is not defined. PR by Séverin
Lemaignan, thanks!

Bump PKGREVISION