No need to build 8.4 now that it's been released.  Add 9.2 instead.
Only run svn cleanup + svn update if the source directory has a .svn
subdirectory.  The source directory might already exist but be empty;
for instance, it could be a tmpfs mount.
%INITIAL_CONFIG contains arrayrefs, so we need to deep-clone it into
%CONFIG; otherwise, modifying e.g. %CONFIG{ENV} will actually modify
%INITIAL_CONFIG{ENV} and thereby contaminate the next job.
Support variant builds, where everything after the first hyphen in the
config name (except for an optional -build suffix) indicates a variant.
It makes a lot more sense to read site.rc after the config than before it.
This allows site.rc to override existing settings, e.g. disable email
reports by clearing RECIPIENTS.  Also bump version and copyright.
Include the config name in the process title.
Allow lower-case letters in environment variable names.
Add support for include statements.
Add variant configurations for building head without clang and bmake.
WITHOUT_CLANG also requires WITH_GNUCXX.
Remove support for cvs and cvsup.
Improve the logic used to determine the default value of the HOSTNAME
configuration variable.

Introduce an NCPU configuration variable and implement similar logic
as for the HOSTNAME configuration variable.

Change the configuration variable substitution syntax from %%FOO%% to
${FOO}.  The old syntax is still supported for backward compatibility,
but is not used internally and is deemphasized in the documentation.

Introduce support for using environment variables in configuration
files.  This requires a fair amount of validation and untainting.

Clean up the man page, especially the list of configuration variables,
and provide more detailed explanations of some of the darker corners
of the code as well as advice about tuning JOBS and NCPU.
Switch from %%FOO%% syntax to ${FOO} syntax.
No need to build 9.2 now that it's been released.
Hack the WORD_OPTIONS validation so strings like i386/pc98 are seen as
valid words.
Add FreeBSD 10.
Add missing platforms: armv6 and mips64.
Restructure the outer and inner loop so results are sorted first
numerically by branch rank, then alphabetically by variant.
Add WITHOUT_CLANG_IS_CC.

Submitted by:	dim
- Add --no-ignore to the "svn stat" command line so we pick up things
  like LINT etc which are normally hidden but can cause surprises.
- Validate and untaint the SVN base URL.
- In spawn(), check whether the command and arguments are tainted so we
  can more easily debug future occurrences.