Fix whitespace issues found by git diff --check, add gitattributes

Set per file type attributes in .gitattributes to fine-tune whitespace
checks.  With the associated cleanups, the tree is now clean for git

doc/src/sgml/sources.sgml

@@ -148,7 +148,7 @@ ereport(ERROR,
     function and does not return to the caller. If the severity level is
     lower than <literal>ERROR</>, <function>ereport</> returns normally.
    </para>
-    
+
    <para>
     The available auxiliary routines for <function>ereport</> are:
   <itemizedlist>