Add --minify option to make_dist.sh

The --minify option allows the callee to specify what InitJS minify method
to use: uglifyjs, uglifyjs2, closure, none.  The "none" option is useful when
build time and dependencies are more important than a few kilobytes.
Choose InitJS minify method explicitly
Merge branch 'dist-option-initjs-minify'

Add an explicit --minify option to the make_dist.sh utility script to
allow more build flexibility.  In particular, "none" removes dependency
on closure or other minifier.
Ditz issue update
Change closure to a fixed version in build

With this change, building an old Duktape version will use a specific
version of the closure compiler, so that changes in the closure compiler
won't trigger unexpected InitJS bugs.  Apparently minifying can sometimes
break code, depending on what options are used.
Add closure-compiler to ignored dirs
Makefile trivia: no '-' for rm -f lines

With -f the rm command should not fail unless something is really wrong,
so wrong that we should stop, so a preceding minus is not necessarily a
good idea.
Merge branch 'fix-closure-version'

Fix closure compiler version for build so that builds are more repeatable.
Ditz issue update