Add properties help to Jamroot.

[SVN r49508]

Jamroot

@@ -9,7 +9,7 @@
 
 # Usage:
 #
-#   bjam [options] [install|stage]
+#   bjam [options] [properties] [install|stage]
 #
 #   Builds and installs Boost.
 #
@@ -56,8 +56,6 @@
 #   --build-dir=DIR         Build in this location instead of building
 #                           within the distribution tree. Recommended!
 #
-#   --toolset=toolset       Indicates the toolset to build with.
-#
 #   --show-libraries        Displays the list of Boost libraries that require
 #                           build and installation steps, then exit.
 #
@@ -93,6 +91,20 @@
 #
 #   --without-<library>     Do not build, stage, or install the specified
 #                           <library>. By default, all libraries are built.
+#
+# Properties:
+#
+#   toolset=toolset         Indicates the toolset to build with.
+#
+#   variant=debug|release   Select the build variant
+#
+#   link=static|shared      Whether to build static or shared libraries
+#
+#   threading=single|multi  Whether to build single or multithreaded binaries
+# 
+#   runtime-link=static|shared      
+#                           Whether to link to static or shared C and C++ runtime.
+#   
 
 # TODO:
 #  - handle boost version