Add strict build flags also for Clang.
Minor updates to txt, minor code fixes

- remove 'make doc'. I believe this was the cause of occassionally broken parallel builds, but I did this one long ago. Documentation is still build with 'make', IIRC.
- fix headerinfo rounding issue
Merge branch 'testing' of https://github.com/nextgen-astrodata/DAL into testing

merge minor txt changes committed from home into minor changes made at work.