Revert patch 7032 (which moved Power_m_p to a separate file)

Good intentions, but not very elegantly done.  Too many people
got annoyed by the warning message.

[[Imported from SVN: r7036]]

dune/common/misc.hh

@@ -20,8 +20,6 @@
 #include <dune/common/deprecated.hh>
 #include "exceptions.hh"
 #include <dune/common/typetraits.hh>
-#warning If you have included misc.hh only for the Power_m_p class please include power.hh instead.
-#include <dune/common/power.hh>
 
 namespace Dune {
 
@@ -67,6 +65,22 @@ namespace Dune {
     return t*t;
   }
 
+  //! Calculates m^p at compile time
+  template <int m, int p>
+  struct Power_m_p
+  {
+    // power stores m^p
+    enum { power = (m * Power_m_p<m,p-1>::power ) };
+  };
+
+  //! end of recursion via specialization
+  template <int m>
+  struct Power_m_p< m , 0>
+  {
+    // m^0 = 1
+    enum { power = 1 };
+  };
+
   //! Calculates the factorial of m at compile time
   template <int m>
   struct Factorial