This silences the pedantic warning messages from gcc 4.8.3

(performance) Possible inefficient checking for 'lmap' emptiness
(warning) Assignment of function parameter has no effect outside the function. Did you forget dereferencing it?
(style) Array index '<xxx>' is used before limits check

the algorithm is not stable yet

use correct types for integral/sum outputs

* improve `CUDA_TARGET_CPU_ARCH` cache initialization,
    allow to override initial value from calling script;
* add `CUDA_TARGET_OS_VARIANT` option to select OS variant;
* add `CUDA_TARGET_TRIPLET` option to select target triplet from
    `${CUDA_TOOLKIT_ROOT_DIR}/targets` folder;
* remove `CUDA_TOOLKIT_TARGET_DIR` option, now it is calculated from
    `CUDA_TARGET_TRIPLET`, the old approach still can be used for compatibility;
* for CUDA 6.5 and newer try to locate static libraries too, because
   in 6.5 toolkit for ARM cross compilation only static libraries are included.