drop __diefunc compat function

It was dropped from portage almost 2 years ago and was last used about 6
years ago, therefore compatibility is no longer needed.

This also fixes a bug where die was called with 3 string arguments (from
a multiline error message in the WORKDIR fallback support for EAPI >= 4)
which were shifted out of scope due to the old code used to shift the
arguments passed from diefunc whiched called die.
make keepdir recursive check similar to doins/dodoc
read correct variable name for cache-formats from repo metadata info
support generating md5-dict caches using pmaint
fix whitespace
use correct variable name
simplify cache-formats fallback check
fix indexing error
minor spelling fix
refactor(pebuild): use iterators where lists aren't required
docs(ebuild/processor): minor spelling and grammar fixes
fix(pmaint): drop repeated 'in' from regen message
refactor(portage_conf): use cache root dir perms to determine writability

If the cache directory has permissions set allowing for writes to occur
they are allowed. Previously this was set via the readonly parameter to
the related mk_simple_cache function.
refactor(ebuild/portage_conf): set full md5-dict cache dir in config

Previously the full path was constructed in the initialization method
related to the md5_cache class, but this simplifies things and allows
the readonly check from the previous commit to work properly starting
from the root cache dir.
fix(util/commandline): minor spelling issue
refactor(ebuild/portage_conf): simplify getting cache parent dir
refactor(setup.py): use globs to avoid explicitly specifying helper dirs

That way we don't have to remember to add more dirs to the list for
future EAPIs.
refactor(setup.py): further distutils package_data simplification

This assumes we want to install every file under
pkgcore/ebuild/eapi-bash as a data file which should generally remain
true.
refactor(ebuild/processor): import used osutils methods instead of module
refactor(eapi-bash): use existing python scripts instead of redundant shims

Instead of using python shim scripts for pinspect and filter-env for
calls from the bash side we use the versions found in PATH. This is done
for non-system installed pkgcore by adding the bin directory (which
already contains the relevant python scripts) of the git repo or
unpacked tarball to PATH.