BoostBook improvements.
* new/boostbook.jam
Move xsl:param out of here. Print nice error message when boost root is not
specified. Don't set TEMPORARY on catalog files, since it prevents catalog
creation now and catalog is not temparary anyway.
Export boostbook to global scope to that "using boostbook" works.
Update dependency scanner for recent changes in build engine.
* new/xsltproc.jam
New feature xsl:path.
(compute-xslt-flags): New rule, with factored out common code.
Use common.variable-setting-command to simplify actions.
[SVN r19028]
Vladimir Prus