Merge pull request pypa#1032 from takluyver/wheel-dist-name-lower

Author: webknjaz

source/specifications/binary-distribution-format.rst

@@ -159,8 +159,12 @@ As the components of the filename are separated by a dash (``-``, HYPHEN-MINUS),
 this character cannot appear within any component. This is handled as follows:
 
 - In distribution names, any run of ``-_.`` characters (HYPHEN-MINUS, LOW LINE
-  and FULL STOP) should be replaced with ``_`` (LOW LINE). This is equivalent
-  to :pep:`503` normalisation followed by replacing ``-`` with ``_``.
+  and FULL STOP) should be replaced with ``_`` (LOW LINE), and uppercase
+  characters should be replaced with corresponding lowercase ones. This is
+  equivalent to :pep:`503` normalisation followed by replacing ``-`` with ``_``.
+  Tools consuming wheels must be prepared to accept ``.`` (FULL STOP) and
+  uppercase letters, however, as these were allowed by an earlier version of
+  this specification.
 - Version numbers should be normalised according to :pep:`440`. Normalised
   version numbers cannot contain ``-``.
 - The remaining components may not contain ``-`` characters, so no escaping