cmDepends: Define DependencyMap instead of DependencyVector

In `cmDepends` use
`typedef std::map<std::string, std::vector<std::string>> DependencyMap`
instead of defining a
`class DependencyVector : public std::vector<std::string>`
and using it in `std::map<std::string, DependencyVector>`.

Since `std::map<std::string, std::vector<std::string>>` is used in various
other places, we now reuse all of it's auto generated methods.  This doesn't
happen when we use `DependencyVector` in a `std::map`, because it is a
different class than `std::vector<std::string>`.

Source/cmDependsJava.h

@@ -8,7 +8,6 @@
 #include "cmDepends.h"
 
 #include <iosfwd>
-#include <map>
 #include <set>
 #include <string>
 
@@ -33,9 +32,9 @@ protected:
   bool WriteDependencies(const std::set<std::string>& sources,
                          const std::string& file, std::ostream& makeDepends,
                          std::ostream& internalDepends) override;
-  bool CheckDependencies(
-    std::istream& internalDepends, const std::string& internalDependsFileName,
-    std::map<std::string, DependencyVector>& validDeps) override;
+  bool CheckDependencies(std::istream& internalDepends,
+                         const std::string& internalDependsFileName,
+                         DependencyMap& validDeps) override;
 };
 
 #endif