buildfarm minimum script versions

Following a suggestion by Tom Lane, I have written some code that will
reject reports from members running very old script versions. In a week
I intend to turn it on and require script version 1.45 as a minimum.
That version is 18 months old. 1 month later I propose to set that to
1.68, which is now 7 months old.

The following members are going to be affected:

kingfisher | 'script_version' => '1.17'
otter | 'script_version' => '1.17'
hare | 'script_version' => '1.45'
thrush | 'script_version' => '1.45'
bear | 'script_version' => '1.57'
grebe | 'script_version' => '1.62'
kite | 'script_version' => '1.62'
stoat | 'script_version' => '1.62'
yak | 'script_version' => '1.62'

cheers

andrew