Log Message:
Update waf to 1.8.17:

NEW IN WAF 1.8.17
-----------------
* Added customizations that enable building whole projects from the build folder \ 
instead of the variant folder
* Added a project generator for Xcode 6 #1648
* Force scanner functions to run after task failures #1660
* Improved the Intel Fortran compiler detection #1655
* Added processing of chmod attributes on subst and rule when provided #1650
* Enabled global_define in conf.check() tests
* Enabled usage of home folder/tilde ~ in Configure.find_files
* Added usage of options.enable_gccdeps when provided by user scripts
* Enabled 'waf -v' to catch invalid string on hcode values in Python3
* Fixed the function names returned by the @conf and @run_once decorators
* Let 'subst' change permissions for all its files with chmod (not just the \ 
first one)
* Added quoting for space-containing-arguments in print_commands.py