always install doxygen files, even if we didn't generate them

[[Imported from SVN: r6759]]

[[Imported from SVN: r6519]]

[[Imported from SVN: r6488]]

[[Imported from SVN: r6455]]

This fixes #803, but leaves us with the ugly situation, that docs in the 
tar balls don't get installed, if doxygen is missing.

[[Imported from SVN: r6435]]

[[Imported from SVN: r6156]]

[[Imported from SVN: r6154]]

[[Imported from SVN: r6134]]

[[Imported from SVN: r6133]]

libtool dummy source trick)

[[Imported from SVN: r6115]]

[[Imported from SVN: r6114]]

[[Imported from SVN: r6113]]

[[Imported from SVN: r6005]]

[[Imported from SVN: r5948]]

[[Imported from SVN: r5937]]

- buildir isn't always defined

: merge to release

[[Imported from SVN: r5895]]

: merge to release

[[Imported from SVN: r5894]]

: merge to release

[[Imported from SVN: r5893]]

for older automake versions

: merge to release

[[Imported from SVN: r5892]]

header-check-ignore

[[Imported from SVN: r5890]]

[[Imported from SVN: r5844]]

[[Imported from SVN: r5843]]

[[Imported from SVN: r5818]]

[[Imported from SVN: r5815]]

* make distcheck work
* make out-of-source builds for tarballs work
... all this only for dune-common...

[[Imported from SVN: r5811]]

[[Imported from SVN: r5804]]

[[Imported from SVN: r5797]]

[[Imported from SVN: r5793]]

- add proper web-install target that seperated recursion and local targets
- move web-install to documentation, so that you can call "make web.install" from top-src
- provide fallback targets, if doxygen and/or wml is missing

[[Imported from SVN: r5792]]

[[Imported from SVN: r5791]]

[[Imported from SVN: r5787]]

[[Imported from SVN: r5785]]

[[Imported from SVN: r5784]]

[[Imported from SVN: r5782]]

[[Imported from SVN: r5770]]

[[Imported from SVN: r5767]]

[[Imported from SVN: r5765]]

[[Imported from SVN: r5763]]

[[Imported from SVN: r5761]]

  now all headerchecks are also tested in the build tests
* add timing facility to check-log
  run
    make check-log LOG_TIMING="time -p"
  to add timings to your test log files

[[Imported from SVN: r5760]]