new compile.el

[Reto Zimmermann <Reto.Zimmermann@synopsys.com>]

How do I transition a major mode (vhdl-mode) to use the new compile.el? 
  From reading the compilation-error-regexp-alist description it sounds 
like it should still work with the old alist but then it doesn't work 
right.  Converting to use compilation-error-regexp-alist-alist is 
problematic because it only seems to accept one regexp per mode, while I 
use several regexps to match error messages of the various VHDL 
compilers that exist.

Any hints at how I can get this to work and all the things that need to 
be changed?

Thanks,
Reto