Don't crash on use of <tag> in directories containing dots.

The <tag> rule if often used in Jamfile like this: <tag>@$(__name__).rule.
The __name__ looks like Jamfile<jamfiles'directory>. When directory has
a dot, we we confused and took the part till the first dot as the
name of module.

Now, such values are processed closer to the definition point, where
we know the name of the module and don't need to guess it by looking at
the name.

Thanks to Juergen Hunold for the bug report.


[SVN r28063]

tools/build

@@ -1 +1 @@
-Subproject commit 707a30f8b1478cb177da97a0564c50921f198360
+Subproject commit 62273e9a85859766cf0734c8ee6dc0dbf4208890