watch 3.3.10: new version and upstream switch

Updated `watch` to the latest version from the procps-ng project, a Debian, Fedora and openSUSE fork of procps. It's more up-to-date than the procps project.
In this version it also supports colored output.
Add AM_LDFLAGS explaination
Enhanced test. Thanks to @mikemcquaid
watch: add 3.3.10 bottle.