Adds some check to treat OOM problems + RDP security fix

Malloc can fail so it will, this patch adds some check in some places
where malloc/strdup results were not checked.

This patch also contains a server side fix for RDP security (credit to nfedera).
The signature len was badly set in the GCC packet. And some other RDP security
oriented fixes are also there.
Merge pull request #1756 from hardening/malloc_checks

Adds some check to treat OOM problems + RDP security fix