MINOR: startup: sort the feature list in haproxy -vv

MINOR: startup: sort the feature list in haproxy -vv

The feature list in haproxy -vv is partly generated from the Makefile
using the USE_* keywords, but it's also possible to add keywords in the
feature list using hap_register_feature(), which adds the keyword at the
end of list. When doing so, the list is not correctly sorted anymore.

This patch fixes the problem by splitting the string using an array of
ist and applying a qsort() on it.