Make AutoLock noncopyable (it would break on copying, anyway).
setting 'char' to be signed by default since some tests fail when it's wrong (e.g. native compilation on ARM Linux)
making the comment less ambigous
disabled samples with driver api
fixed gpu module build on arm platform

links with CUDA driver library only if we use video encoding/decoding
Merge pull request #940 from SpecLad:autolock
Merge pull request #893 from jet47:gpu-arm-fixes
Merge pull request #941 from apavlenko:signed_char
Merge pull request #947 from jet47:fix-gpu-arm-build