added support for features array to toolchains

tools/targets.py

@@ -58,7 +58,7 @@ def cached(func):
 class Target:
     # Cumulative attributes can have values appended to them, so they
     # need to be computed differently than regular attributes
-    __cumulative_attributes = ['extra_labels', 'macros']
+    __cumulative_attributes = ['extra_labels', 'macros', 'features']
 
     # {target_name: target_instance} map for all the targets in the system
     __target_map = {}

tools/toolchains/__init__.py

@@ -324,6 +324,11 @@ class mbedToolchain:
 
             # Add target's symbols
             self.symbols += self.target.macros
+            # Add target's hardware
+            try :
+                self.symbols += ["DEVICE_" + feature + "=1" for feature in self.target.features]
+            except AttributeError :
+                pass
             # Add extra symbols passed via 'macros' parameter
             self.symbols += self.macros