boostbook.jam; Make it possible to configure where to find boostbook files.

boostbook-config.jam; Find boostbook files using Boost install key.
quickbook-config.jam; Auto config of quickbook tool.


[SVN r28464]

tools/build

@@ -1 +1 @@
-Subproject commit f191d632c37072dfeba5043a43d7934dc5e803ff
+Subproject commit 77476676e5eabccaf6f4d5a63e76d5cc59f9c91b