enums: omit trailing comma for portability

enums: omit trailing comma for portability

Without this patch at least IBM VisualAge C 5.0 (I have 5.0.2) on AIX
5.1 fails to compile git.

enum style is inconsistent already, with some enums declared on one
line, some over 3 lines with the enum values all on the middle line,
sometimes with 1 enum value per line... and independently of that the
trailing comma is sometimes present and other times absent, often
mixing with/without trailing comma styles in a single file, and
sometimes in consecutive enum declarations.

Clearly, omitting the comma is the more portable style, and this patch
changes all enum declarations to use the portable omitted dangling
comma style consistently.

Signed-off-by: Gary V. Vaughan <gary@thewrittenword.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>