gnustep-base library versioning

[Larry Campbell]

gnustep-base specifies an INTERFACE_VERSION that includes its minor  
version number. This means that I have to relink everything whenever  
I deploy a new version of gnustep-base. This is really rather  
impractical, and I wonder whether we couldn't change INSTALL_VERSION  
to include only the major version number (and, of course, make no  
backwards-incompatible changes during minor version upgrades).

The current behavior, where every program needs to be relinked and  
redeployed whenever gnustep-base is updated, is a significant  
inhibitor to the adoption of gnustep where I work.

- lc