* The search for a matching interval in a table of break-points was optimized.
  The lookup function now looks first to the previous interval, then the
  intervals below and above the previous one. Only if these intervals don't
  match it performs a binary search across the while break point table.
* If the functions csm_x, csm_y or csm_z are called with the same values as the
  last time, they do not perform any calculation but return the previous value
  from their internal cache.

lookup_1d_functiontable now handles the case of a table with a single
point (xp,yp) correctly. It then returns the associated yp for any value of
x. Before this change, it returned NAN for x!=xp and yp for x==xp.

Additionally, the functions lookup_1d_functiontable and
lookup_2d_functiontable now return NAN (not a number) in case the table
doesn't contain any values.

Also convert cvtRecord.html to cvtRecord.rst, and
integrate the csm doxygen generated API docs.

This was needed for better portability.

File-specific comments:

./csmApp/Doxyfile.external:
  Converted to the new doxyfile format
  
./csmApp/Doxyfile.internal:
  Converted to the new doxyfile format

  + bugfix with respect to the on-hold function: The "last" field
    of the csm_Function structure has to exist for each type of
    function that can be applied to the structure, one for
    csm_x(), one for csm_y(), one for csm_z(), for csm_dx() and
    csm_dy(). With only one field, it may happen for example,
    that when "on_hold" is used, csm_x() returns the last returned
    value of csm_y().
  + bugfix with respect to multithreading use:
    the semaphore used in functions like csm_x(), csm_y() and so
    on was given just before a return-statement which did a read-access
    on the function structure. This lead to a race condition where
    it was possible that one call of csm_x() returned the value of
    another call of csm_x() which was called by another task. Together
    with "last" field bug mentioned above, csm_x() could even return
    the value of the last csm_y() call, which is fatal...

* usage of psem (portable semaphores) can now be selected
* usage of DBG, errlogPrinf or printf can now be selected
  define USE_DBG and USE_ERRLOGPRINTF accordingly
* prepared for Linux (undefine B_VXWORKS for this,
  set USE_DBG 0, USE_ERRLOGPRINTF 0 and USE_PSEM 1
* memory leak error was fixed in csm_read_2d_table

debug messages are now printed asynchronously
(if used at all)

a new function, csm_free was added. This function releases all
memory and finally releases the memory of the csm_function object
itself.

a new function, csm_clear was added. This function releases all
  memoty an csm_function occupies and sets its value to CSM_NOTHING