ui-repolist: Add an id for each section

This allows header= overrides to decorate section names (for instance
handling collapsible sections).

Signed-off-by: Andy Doan <andy.doan@linaro.org>
diff --git a/ui-repolist.c b/ui-repolist.c
index cee6543..0dff9f0 100644
--- a/ui-repolist.c
+++ b/ui-repolist.c
@@ -364,8 +364,8 @@
 		    (last_section != NULL && section == NULL) ||
 		    (last_section != NULL && section != NULL &&
 		     strcmp(section, last_section)))) {
-			htmlf("<tr class='nohover-highlight'><td colspan='%d' class='reposection'>",
-			      columns);
+			htmlf("<tr id='%s' class='nohover reposection'><td colspan='%d' class='reposection'>",
+			      section, columns);
 			html_txt(section);
 			html("</td></tr>");
 			last_section = section;