Bug 1098: improve invalid pcre/R handling

When not using a file_data or similar 'sticky buffer', a pcre/R option
needs a content in the same buffer.

Prscript:
- PR build: https://buildbot.suricata-ids.org/builders/inliniac/builds/326
- PR pcaps: https://buildbot.suricata-ids.org/builders/inliniac-pcap/builds/241