gitweb: Add author information to commitdiff view

Add subroutine git_print_authorship to print author and date of
commit, div.author_date style to CSS, and use them in git_commitdiff.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/gitweb/gitweb.css b/gitweb/gitweb.css
index afd9e8a..eb9fc38 100644
--- a/gitweb/gitweb.css
+++ b/gitweb/gitweb.css
@@ -116,6 +116,13 @@
 	font-style: italic;
 }
 
+div.author_date {
+	padding: 8px;
+	border: solid #d9d8d1;
+	border-width: 0px 0px 1px 0px;
+	font-style: italic;
+}
+
 a.list {
 	text-decoration: none;
 	color: #000000;