mpf_round compilation issue note

[Manuel Salvadores]

Hello,

If you build 4store (1.1.3) on a Debian distribution with the latest
rasqal source distribution (0.9.25) and you encounter a compilation
error with a message that says that there's something wrong with the
"mpf_round" function then patch rasqal with [1] and rebuild rasqal and
4store.

There might be a cleaner way to do it but this worked for me. Just to
leave a note about it.

Manuel

[1] https://github.com/dajobe/rasqal/commit/c5126ea60f4556a402c6fb74f0edae04ddcb796b.patch