zygo: version strings that begin with a letter are now an error

zygo: version strings that begin with a letter are now an error
(cherry picked from commit 786b25291717a7af315b2b3a0e3b3defbae118ee)
(cherry picked from commit 6e6f2a774fd0b147b353b79e6a5e8a3edc39174a)

Conflicts:

	zygo/make-kernel
(cherry picked from commit 7d994a82621ffa414bf8860a24536333d799717c)

Conflicts:

	zygo/make-kernel
(cherry picked from commit 6ef9e28c847d68e4e00ab11c55301aa95ae32624)

Conflicts:

	zygo/make-kernel
(cherry picked from commit 8b5c308ccbc6c21fe85d5f4ace32534960ed3813)

Conflicts:

	zygo/make-kernel