Changes:

Most important:

Parallel installation with ALBERTA-1.X works fine now. To achieve this
the following changes were necessary:

- headers are installed in PREFIX/include/alberta2/
- libalberta_util.XX -> libalberta2_util.XX
- Makefile.alberta is installed in PREFIX/share/alberta2/ 
- package name was changed to alberta2
- libtool.alberta -> libtool.alberta2, intalled in PREFIX/libexec/ as usual
- alberta_grape etc. -> alberta2_grape

No need to change the names of other add-ons because they were not
present in ALBERTA-1.X.

Further changes:

- The preprocessor symbol DEBUG is quite overloaded. It has been
  changed to ALBERTA_DEBUG, the Makefile.alberta has been changed
  accordingly, and (hopefully) all source files using DEBUG.

- "make dist" was broken. This was caused by automake
  brain-damagedness: adding a directory to EXTRA_DIST results in
  copying that directory TWICE to the distribution directory, however,
  "make dist" likes to create several file read-only, so the second
  attempt to copy the directory contents would fail (permission denied).

  Also, some of the auto-generated files were not removed by "make
  distclean" which led to a failing "make distcheck".

This mess was comitted by cH (aka alberta on pizza).