Convert macros from plain QByteArray to a vector of structs

The old code model expected the macros as C++ formatted text
("#define Foo 42) but newer targets like the Clang codemodel expect key
value arguments like "-DFoo=42". So instead of parsing the text again and
again we use an abstract data description.

Task-number: QTCREATORBUG-17915
Change-Id: I0179fd13c48a581e91ee79bba9d42d501c26f19f
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cmakeprojectmanager/cmakeproject.cpp

@@ -559,7 +559,7 @@ void CMakeBuildTarget::clear()
     targetType = UtilityType;
     includeFiles.clear();
     compilerOptions.clear();
-    defines.clear();
+    macros.clear();
     files.clear();
 }