doc: pretty-formats: separate parameters from placeholders

Commit a57523428b (pretty: support padding placeholders, %< %> and %><,
2013-04-19) introduced columnated place holders. These placeholders
can be confusing as they contain `<` and `>` characters as part
of their placeholders adjacent to the `<N>` parameters.

Add spaces either side of the `<N>` parameters in the title line.
The code (strtol) will consume any spaces around the number values
(assuming they are passed as a quoted string with spaces).
Note that the spaces are optional.

Subsequent commits will clarify other confusions.

Signed-off-by: Philip Oakley <philipoakley@iee.email>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/pretty-formats.txt

@@ -152,8 +152,11 @@ The placeholders are:
 				  truncate at the beginning (ltrunc),
 				  the middle (mtrunc) or the end
 				  (trunc) if the output is longer than
-				  N columns.  Note that truncating
+				  N columns.
+				  Note 1: that truncating
 				  only works correctly with N >= 2.
+				  Note 2: spaces around the N
+				  values are optional.
 '%<|( <N> )':: make the next placeholder take at least until Nth
 	     columns, padding spaces on the right if necessary
 '%>( <N> )', '%>|( <N> )':: similar to '%<( <N> )', '%<|( <N> )' respectively,