Rename QContiguousCache allocate and free functions to say "Data"

Rename QContiguousCache allocate and free functions to say "Data"

The important change is to use functions not called malloc and
free. On some old systems or under some weird circumstances, they
might be #defined to something different. More importantly, this
allows us to quickly verify whether we're using the stdlib.h functions
in our public headers.

Change-Id: I66b963ac2bc75d64028c04542e62a929e4b36b19
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>