Improve xbt_os_thread_setstacksize().

If it fails with the requested size, try again with a multiple of PTHREAD_STACK_MIN.
Correctly remember when "contexts/stack_size" was not set by the user.

The main effect is to use the system default for thread stack size.
There is no reason to trim the output.
Fix spacing issues in tesh files.
Few updates to INSTALL file.

SVN replaced by Git, Ruby bindings don't belong to the main archive,
add options for Scala bindings and model-checker.
Run tesh self tests in ${CMAKE_BINARY_DIR}/bin.
Put tests for tesh output sort in a separate file.
Rename file for consistency.
Add more multiline tests for tesh.  Also check for failures.
Add some tests for tesh "output sort".
Remove spurious spaces in tesh output.
There is no reason to trim the output in tesh.pl too.
Typo.
Add suport for sort prefix length in tesh.pl.
Tesh sort removes empty lines, do it also with tesh.pl.
Align address on page boundary (fails on kfreebsd otherwise).
Add calls to smpi_bench_{end,begin} in PMPI_Wtime.

Without this change, doing something like the following always
gives a duration of zero:

    ...
    start = MPI_Wtime();
    // big computation...
    end = MPI_Wtime();
    duration = end - start;
    ...

Make sure that no calls to smpi_bench are made when process is not
between init and finalize, nor during sample blocks.