Merge changes in Trunk:

  Simplify regex_timer to eliminate regression failure.
  Rename extern "C" function to have a "boost_" prefix.
  Fix recursive-expression related bug, and update tests to match.

[SVN r58885]

libs/regex

@@ -1 +1 @@
-Subproject commit e41acbc33f7a4169c9d3d9c4c9366f235985cce7
+Subproject commit fc6408426d15f62c6857b932af1f479e90ca5a9b