[lttng-dev] Update of configure script

[Jonathan Rajotte]

Hi all,

The following three patches update the autoconf script making sure we have all
the requirements at build time. Nothing special here, simply good practice. 

Cheers!

[PATCH babeltrace 1/3] Configure: add missing check for used funcs
[PATCH babeltrace 2/3] Configure: add check on headers
[PATCH babeltrace 3/3] Configure: add check for type