camera: minor constness

This commit fixes constness of camera getters, and changes a few
arguments into const references.
timing: constness fix
Merge pull request #49 from zerhacken/minor-fixes

Minor const correctness fixes from zerhacken
Only read from input data from debug message when WRITING.

Fixes submitted auto-crash-dump "report_2014.05.07_16.39.37_408"
Don't call thread exception handlers on mono that aren't implemented yet