Add pcre devel package for Horizon

pyScss python module uses pcre if available for performance
and it is better to be installed.
This commit adds it for files/{apts,rpms}/horizon.

Change-Id: If711fa222d3f395efd670334c8a84f35d195dc25
diff --git a/files/apts/horizon b/files/apts/horizon
index 03df3cb..5d06928 100644
--- a/files/apts/horizon
+++ b/files/apts/horizon
@@ -17,3 +17,4 @@
 python-coverage
 python-cherrypy3 # why?
 python-migrate
+libpcre3-dev  # pyScss