[Issue #792] Fix compilation warnings - some warnings addressed

[lr-morales]

This PR should address some of the compilation warnings produced when building JdeRobot, mostly non-return (as best as could without changing function return type) and unsigned comparison warnings.

[aitormf]

all works for me

[fqez]

Nice job

@lr-morales are you planning on keep adressing warnings? Or should we merge this already?

Cheers!

[lr-morales]

I have located some more "easy-to-solve" warnings, we can wait them before merging. I can comment again when I finish or feel that solving more warnings would take long in order to merge the ones already cleared and checked.

[lr-morales]

Hello,

this PR should be ready about the "easy-to-solve" warnings, the remaining warnings should be the ones pointed at the issue #792.
@fqez, @aitormf: I think these should be reviewed and merge first and then start addressing the remaining ones.

[aitormf]

It's all Ok for me, good job @lr-morales