Documentation update.

    * boost_build_v2.html: Extend feature description. Change wordings in
        some places.
    * new/feature.jam: Remove comments that are now in boost_build_v2.html.


[SVN r14782]

tools/build

@@ -1 +1 @@
-Subproject commit 5375bed958f75e818ff130cb63b09acb813506a9
+Subproject commit a0cfe4076e0dca4a67ce1ec0c817eacfd4a8ea3d