Fix generation of COMPILE_DEFINITIONS in DependInfo.cmake.

As INTERFACE_COMPILE_DEFINITIONS are now possible, we can have
situations like this:

 add_library(foo ...)
 add_library(bar ...)
 target_link_libraries(foo bar)

 target_compile_definitions(bar INTERFACE SOME_DEF)

The INTERFACE_COMPILE_DEFINITIONS of bar determine how foo should be
compiled, and if they change, foo should be rebuilt.

Additionally, as of commit d1446ca7 (Append the COMPILE_DEFINITIONS
from the Makefile to all targets., 2012-09-17), we don't need to
read definitions from the makefile if we read them from the target,
so also de-duplicate the cached info.

The DependInfo for INTERFACE_INCLUDE_DIRECTORIES is already handled
correctly.

Source/cmLocalUnixMakefileGenerator3.cxx

@@ -1961,34 +1961,17 @@ void cmLocalUnixMakefileGenerator3
     }
 
   // Build a list of preprocessor definitions for the target.
-  std::vector<std::string> defines;
-  {
-  std::string defPropName = "COMPILE_DEFINITIONS_";
-  defPropName += cmSystemTools::UpperCase(this->ConfigurationName);
-  if(const char* ddefs = this->Makefile->GetProperty("COMPILE_DEFINITIONS"))
-    {
-    cmSystemTools::ExpandListArgument(ddefs, defines);
-    }
-  if(const char* cdefs = target.GetProperty("COMPILE_DEFINITIONS"))
-    {
-    cmSystemTools::ExpandListArgument(cdefs, defines);
-    }
-  if(const char* dcdefs = this->Makefile->GetProperty(defPropName.c_str()))
-    {
-    cmSystemTools::ExpandListArgument(dcdefs, defines);
-    }
-  if(const char* ccdefs = target.GetProperty(defPropName.c_str()))
-    {
-    cmSystemTools::ExpandListArgument(ccdefs, defines);
-    }
-  }
+  std::set<std::string> defines;
+  this->AppendDefines(defines, target.GetCompileDefinitions());
+  this->AppendDefines(defines, target.GetCompileDefinitions(
+                                            this->ConfigurationName.c_str()));
   if(!defines.empty())
     {
     cmakefileStream
       << "\n"
       << "# Preprocessor definitions for this target.\n"
       << "SET(CMAKE_TARGET_DEFINITIONS\n";
-    for(std::vector<std::string>::const_iterator di = defines.begin();
+    for(std::set<std::string>::const_iterator di = defines.begin();
         di != defines.end(); ++di)
       {
       cmakefileStream