* Rename prepare_sources.py to configure.py; the operation is similar to
autoconf ./configure so the association is useful.
* Rename make_dist.py to dist.py.
* Generate only one source set (combined or separate) for one run of
configure.py.
* Change dist.py to run configure.py three times to generate the default
source sets.
* Use an autodeleted temporary directory for preparing sources, which
removes some of the manual temporary file handling.
- Disable JSON.stringify() fastpath by default
- Rework to use DUK_USE_ALIGN_BY config option
- Replace previous DUK_USE_ALIGN_4 and DUK_USE_ALIGN_8 with a cleaner
DUK_USE_ALIGN_BY config option (allowed values 1, 4, 8)
- Add fastpath tag in anticipation of automatic fastpath suggestions
or warnings