- Fixed incorrect environment variable name in comment.

- Added some additional documentation to the FILES and IMAGES variables.

- Added SUBJECT_CODE required variable.

- Fixed tidying and cleaning.

- Added support for hiding and showing answers in general documents ...

(especially useful for assignments).

- Enabled multiple base documents.

- Added documentation on alternative uses of the SLIDES, etc., variables.

- Removed obsolete OmniGraffle references.

- Removed obsolete prerequisites.

- Updated makefiles for new common infrastructure.

- Added paper and chapter variables files to prerequisites.

- Fixed combined prerequisite variable names (d'oh!)

- Fixed figures prerequisite (put in FIG_IMAGES instead of FIG_FILES). ...

- Added variables for combined document prerequisites.

- Added infrastructure files for figures and fixed slides variable.

- Added default spec for shared infrastructure files.

- Added INSTALL variables.

- Updated comments to match usage.

- Added new makefile infrastructure for general documents. ...

- Created include files for various "standard" items (paths, rules, etc.).
  These will ultimately be used by all the other make include files in
  order to promote standardisation and consistency.
- Removed obsolete Perl script for handling document includes.

- Added default vpath for .pict.

- Added .svg to list of standard suffixes.

- Added support for Inkscape SVG files.

- Added case_study and introduction items to default patterns.

- Moved .aux files from TIDY_FILES to CLEAN_FILES.

- Added SLIDE_FILES and FIG_FILES variables for miscellaneous dependencies. ...

- Added default rules for {.png,.jpg} -> .graffle and .pict -> .png.

- Updated the list of standard suffixes as well.

- Updated list of standard vpaths.

- Split apart custom rules and variables.

- Changed order of centralised rule loading.

- Removed redundant target for regenerating patterns files.

- Deleted a couple of rogue vpaths that crept in.