Teach base-directory about pathnames, strings.
Add FIRST-FORM-OF.
Add SAVE-FORMS, SAVE-FORM.
Add a cache for system-file-magic.
Add RUN-OUTPUT-LINE to get the first line of command output.
Add the start of an HTML failure report.

When a build fails, this is meant to make it easy for interested helpers
to pinpoint the problem, report bugs, and offer solutions.
Move recrank into its own file.

This is so it can generate an HTML failure report.
Add IN-ANONYMOUS-DIRECTORY.
Cache system-file-magic failures, too.
Add system source relativity features.
Take SBCL contribs out of build process.

Several projects implicitly depend on sb-* contribs,
e.g. sb-bsd-sockets, sb-posix, etc. This relationship was masked by the
fact that quicklisp-controller preloaded those contribs.

The contribs are no longer preloaded, so simple implicit dependencies
signal a build failure.
By default, upload a HTML failure report after recrank.