[svn-r29759] Purpose: Code improvements

Description:
    - Changed object in catch statements to reference
    - Replaced old-style casts or reinterpret_cast with static_cast
    - Removed unused name H5Library::need_cleanup
    - Removed Exception::printError from documentation
Platforms tested:
    Linux/32 2.6 (jam)
    Linux/64 (platypus)
    Darwin (osx1010test)

c++/src/H5DataSet.cpp

@@ -781,7 +781,7 @@ void DataSet::p_setId(const hid_t new_id)
     try {
         close();
     }
-    catch (Exception close_error) {
+    catch (Exception& close_error) {
         throw DataSetIException(inMemFunc("p_setId"), close_error.getDetailMsg());
     }
    // reset object's id to the given id
@@ -841,7 +841,7 @@ DataSet::~DataSet()
     try {
 	close();
     }
-    catch (Exception close_error) {
+    catch (Exception& close_error) {
 	cerr << "DataSet::~DataSet - " << close_error.getDetailMsg() << endl;
     }
 }