Miscellaneous code cleanup

Description:
    - Removed two inadvertently-added Group constructors in the header file.
      There was no implementation.
    - Removed deprecated H5Location and H5Object constructors that take an
      existing ID.
    - Miscellaneous improvements in comments, including updating URLs.
Platforms tested:
    Linux/32 2.6 (jam)
    Linux/64 (jelly)
    Darwin (osx1010test)

c++/src/H5Object.h

@@ -36,9 +36,8 @@ namespace H5 {
                 into H5Object.  This way, C functions that takes attribute id
                 can be in H5Location and those that cannot take attribute id
                 can be in H5Object.
-
-    Inheritance: H5Location -> IdComponent
 */
+// Inheritance: H5Location -> IdComponent
 
 // Define the operator function pointer for H5Aiterate().
 typedef void (*attr_operator_t)(H5Object& loc/*in*/,
@@ -113,7 +112,7 @@ class H5_DLLCPP H5Object : public H5Location {
         // removal does not raise any problems in two 1.10 releases.
 
         // Creates a copy of an existing object giving the object id
-        H5Object(const hid_t object_id);
+        // H5Object(const hid_t object_id);
 
         // Copy constructor: makes copy of an H5Object object.
         // H5Object(const H5Object& original);