* AutotoolsPackage: added configure_directory to permit build out of source. The configure script executable is now invoked with an absolute path. Modified a few packages accordingly.
* build_systems: functions returning directories are now properties
* build_systems: fixed issues with tcl and tk
* AutotoolsPackage: reworked recipe for autoreconf
* MakefilePackage: changed build_args and install_args for consistency with #2464
openblas: derives from MakefilePackage
* MakefilePackage: changed default edit behavior
Modifications :
- added EditableMakefile to PackageBase subclasses
- astyle modified as an example
- preliminary hook to stop at a certain phase of install