Add URL parameter 'context' for changing the number of context lines in diffs

The new ctx.qry.context variable is picked up by cgit_print_diff(), and
passed via cgit_diff_files() to Git's diff machinery.

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>
diff --git a/cgit.c b/cgit.c
index 2c3ad73..e9bafb5 100644
--- a/cgit.c
+++ b/cgit.c
@@ -250,6 +250,8 @@
 		ctx.qry.period = xstrdup(value);
 	} else if (!strcmp(name, "ss")) {
 		ctx.qry.ssdiff = atoi(value);
+	} else if (!strcmp(name, "context")) {
+		ctx.qry.context = atoi(value);
 	}
 }