[Mitgcm-support] .gnemakerc

[mitgcm-support at dev.mitgcm.org]

We should start including .genmakerc 
files for reference/verification experiments?
It is useful to know what packages an experiment
uses.

In prep. I am changing genmake to 

 o introduce reserved package name of all which allows
set DISABLE = ( all ) and/or
set ENABLE  = ( all ) 
ENABLE should take precdence over DISABLE.
Sound OK?

Chris