Fix some issues found with clang-tidy (#4353)

* directoryiterator: Fix missing inline

Add missing inline to inline function.

This was found with clang-tidy check:  misc-definitions-in-headers

* Convert deprecated throw() to noexcept

throw() has been deprecated in standar in C++17. It has been removed in
C++20. Code still compiles but let's just define these at those should
be.

These where found with clang-tidy check: modernize-use-noexcept

* Fix unnecessary copy initializations

Clang-tidy did find these with check:

  performance-unnecessary-copy-initialization

* Fix some strings not references

Looks like these are just missing reference marks.

---------

Co-authored-by: Kari Argillander <kari.argillander@fidelix.com>

Data/PostgreSQL/src/PostgreSQLException.cpp

@@ -45,7 +45,7 @@ PostgreSQLException::PostgreSQLException(const PostgreSQLException& anException)
 }
 
 
-PostgreSQLException::~PostgreSQLException() throw()
+PostgreSQLException::~PostgreSQLException() noexcept
 {
 }