Fix missing libuev in 'make dist' from 1.4 and 1.5 and bump version to 1.6

Since the introduction of libuev the 'make dist' target has failed to
include the libuev subdirectory.  This is due to the 'git archive'
command unfortunately not supporting git submodules.

This commit changes 'make dist' to use Kentzo's git-archive-all from
https://github.com/Kentzo/git-archive-all

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>