Resolves #7251

Minor fix in MatAllocator::upload
Minor fix in MatAllocator::copy
Minor fix in setSize function
Minor fix in Mat::Mat
Minor fix in cvMatNDToMat function
Minor fix in _InputArray::getMatVector
Minor fix in _InputArray::getUMatVector
Minor fix in cv::hconcat
Minor fix in cv::vconcat
Minor fix in cv::setIdentity
Minor fix in cv::trace
Minor fix in transposeI_ template function
Minor fix in reduceC_ template function
Minor fix in sort_ template function
Minor fix in sortIdx_ template function
Minor fix in cvRange function
Minor fix in MatConstIterator::seek
Minor fix in SparseMat::create
Minor fix in SparseMat::copyTo
Minor fix in SparseMat::convertTo
Minor fix in SparseMat::convertTo
Minor fix in SparseMat::ptr
Minor fix in SparseMat::resizeHashTab
Fixes indentation

In cases where the signaure string contains a terminating character,
the std::string member function size returns a smaller value than the
allocated string. In these cases, if you then try to use substr,
you will get an out_of_range exception. This patch remedies the problem.

This patch implements the PAM image format as defined at:
http://netpbm.sourceforge.net/doc/pam.html

The PAM format provides a generic means for storing 2 dimensional information.
This is useful for opencv since there are cases where data gets translated into
non standardized formats, which makes it difficult to store and load this information.

* Improve Canny by using _mm_movemask_epi8 to find next pixel magnitude greater than lower threshold. Added parallelized finalPass to Canny with variable gradients. Little changes in finalPass.

* Some things fixed

  * use v_float16x4 (universal intrinsic) instead of raw SSE/NEON implementation
  * define v_load_f16/v_store_f16 since v_load can't be distinguished when short pointer passed
  * brush up implementation on old compiler (guard correctly)
  * add test for v_load_f16 and round trip conversion of v_float16x4
  * fix conversion error

Fixed video input argument.

  * use universal intrinsic for accumulate series using float/double
  * accumulate, accumulateSquare, accumulateProduct and accumulateWeighted
  * add v_cvt_f64_high in both SSE/NEON
  * add test for conversion v_cvt_f64_high in test_intrin.cpp
  * improve some existing universal intrinsic by using new instructions in Aarch64
  * add workaround for Android build in intrin_neon.hpp