Log Message:
Update waf to 1.8.19:

NEW IN WAF 1.8.19
-----------------
* Fixed the Intel Fortran compiler detection on Windows systems #1681
* Fixed the detection of newer Sun compilers #1686
* Fixed the detection of NAG Fortran compilers #1684
* Fixed missing variable dependencies of the form ARCH_ST used in \ 
${ARCH_ST:ARCH} expressions
* Added conf.check(..., comment='some text') to document configuration headers