libclient/*: use new version of ASSERT macros

Now, instead of a "custom" error checking we use the
new verison of ASSERT macros (introduced in commit
d1cb76815) which allow us to set the "err" variable
in a more generic way.
hal/msg/*: convert error check to ASSERT macros

Now, instead of a "custom" error checking we use the
new verison of ASSERT macros (introduced in commit
d1cb76815) which allow us to set the "err" variable
in a more generic way.

This together with commit b487515e4 fixes #15 github
issue.