uniform treatment of ISABELLE_HOME/contrib vs. ISABELLE_HOME/..;
syntax: glob
*~
*.class
*.jar
.DS_Store
syntax: regexp
^heaps/
^browser_info/
^doc-src/.*\.aux
^doc-src/.*\.bbl
^doc-src/.*\.blg
^doc-src/.*\.dvi
^doc-src/.*\.idx
^doc-src/.*\.ind
^doc-src/.*\.log
^doc-src/.*\.out
^doc-src/.*\.rai
^doc-src/.*\.rao
^doc-src/.*\.toc