Ignore spaces after 'section:' for quickbook 1.5+ Refs #2712

And warn when section id is empty after colon.

[SVN r55911]

tools/quickbook

@@ -1 +1 @@
-Subproject commit 56e4e76941989de65a00edcd2efcc6ccc4fc6064
+Subproject commit 3b839f1eb09e9c38868c955d68107f5a5d739eea