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/syntax.sgml

@@ -1620,7 +1620,7 @@ SELECT
     count(*) AS unfiltered,
     count(*) FILTER (WHERE i < 5) AS filtered
 FROM generate_series(1,10) AS s(i);
- unfiltered | filtered 
+ unfiltered | filtered
 ------------+----------
          10 |        4
 (1 row)