Added xpressive quickbook dependency.

[SVN r31336]

doc/Jamfile.v2

@@ -14,6 +14,7 @@ boostbook doc : src/boost.xml
      <dependency>../libs/static_assert/doc//static_assert
      <dependency>../libs/foreach/doc//foreach
      <dependency>../libs/xpressive/doc//autodoc.xml
+     <dependency>../libs/xpressive/doc//xpressive
      <dependency>../more/whos_using//using
      <implicit-dependency>../libs/functional/hash/doc//hash
      <implicit-dependency>../libs/type_traits/doc//type_traits
@@ -25,3 +26,4 @@ boostbook doc : src/boost.xml
     ;
 
 
+