Merged in thosrtanner/trt-scons-sig-suppress (pull request #390)

diff --cc src/CHANGES.txt
index ab6797af94cc80bcd39d5eb93c2b73abcc384e64,ad53d7da4209492d0f629992fff2f3b085de6986..fd41a75c139c76827f248c280770c50c8e47bf5b
--- 1/src/CHANGES.txt
--- 2/src/CHANGES.txt
+++ b/src/CHANGES.txt
@@@ -88,22 -62,8 +88,26 @@@ may cause rebuilds.  In no case should 
      - Fixed PCHPDBFLAGS causing a deprecation warning on MSVC v8 and later when
        using PCHs and PDBs together.
  
++
 +  From Richard West:
 +    - Added nested / namespace tool support
 +    - Added a small fix to the python3 tool loader when loading a tool as a package
 +    - Added additional documentation to the user manual on using toolpaths with the environment
 +      This includes the use of sys.path to search for tools installed via pip or package managers
 +    - Added support for a PyPackageDir function for use with the toolpath
 +
 +  From Russel Winder:
 +    - Reordered the default D tools from "dmd, gdc, ldc" to "dmd, ldc, gdc".
 +    - Add a ProgramAllAtOnce builder to the dmd, ldc, and gdc tools. (PR #448)
 +    - Remove a file name exception for very old Fedora LDC installation.
 +    - gdc can now handle building shared objects (tested for version 6.3.0).
 +    - Remove establishing the SharedLibrary builder in the dmd, ldc, and gdc
 +      tools, must now include the ar tool to get this builder as is required for
 +      other compiler tools.
 +    - Add clang and clang++ tools based on Paweł Tomulik's work.
++ 
+   From Tom Tanner:
+     - Allow nested $( ... $) sections
  
  RELEASE 2.5.1 - Mon, 03 Nov 2016 13:37:42 -0400
  

diff --cc src/engine/SCons/ActionTests.py
Simple merge

diff --cc src/engine/SCons/Subst.py
Simple merge

diff --cc src/engine/SCons/SubstTests.py
Simple merge