distscript: port back to sh (from csh)

Also remove the LS_COLORS workaround for the csh bug.

(cherry picked from commit 143e27248f928797e2e8532747386c67c9f8d873)
distscript: ensure to copy entire doxygen-doc to the distdir

Including the trailing / on the directory name seems to make OS X "cp
-rpf" not actually copy the directory.  Shrug.  So just remove the
trailing slash, the entire directory is copied, and "make distcheck"
is happy again.

(cherry picked from commit 8a17908ad7fc966f8f40510c13a08ce71b31b335)
distscript: make it work on Linux, OS X, and Solaris

(cherry picked from commit 4cf1ec7e41bf66365759585aed0e7fc0ffc25c1f)