toolset.using preserves current project (#407)

Using project rule preserves the current project, and toolset.using does not. The problem is that the former is not available in modules that are not projects, and so one has to preserve the current project manually, just in case. I don't think there is ever any point in not preserving the current project when initializing a toolset module, so this change pushes this responsibility on toolset.using.

src/build/project.jam

@@ -1276,8 +1276,6 @@ module project-rules
     {
         import toolset ;
 
-        local saved-project = [ modules.peek project : .current-project ] ;
-
         # Temporarily change the search path so the module referred to by
         # 'using' can be placed in the same directory as Jamfile. User will
         # expect the module to be found even though the directory is not in
@@ -1290,13 +1288,6 @@ module project-rules
             $(9) : $(10) : $(11) : $(12) : $(13) : $(14) : $(15) : $(16) : $(17)
             : $(18) : $(19) ;
         modules.poke : BOOST_BUILD_PATH : $(x) ;
-
-        # The above might have clobbered .current-project in case it caused a
-        # new project instance to be created (which would then automatically
-        # get set as the 'current' project). Restore the correct value so any
-        # main targets declared after this do not get mapped to the loaded
-        # module's project.
-        modules.poke project : .current-project : $(saved-project) ;
     }
 
     rule import ( * : * : * )

src/build/toolset.jam

@@ -39,9 +39,18 @@ if --ignore-toolset-requirements in [ modules.peek : ARGV ]
 #
 rule using ( toolset-module : * )
 {
+    local saved-project = [ modules.peek project : .current-project ] ;
+
     import $(toolset-module) ;
     $(toolset-module).init $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) : $(9)
         ;
+
+    # The above might have clobbered .current-project in case it caused a
+    # new project instance to be created (which would then automatically
+    # get set as the 'current' project). Restore the correct value so any
+    # main targets declared after this do not get mapped to the loaded
+    # module's project.
+    modules.poke project : .current-project : $(saved-project) ;
 }