Set istream flags to 0 in old_deserialize_floating_point.  This was flagged by [[nodiscard]] warning in MS compiler.

Fixes #1188

any BLAS or LAPACK.  Instead, let it get determined at mex load time so that
it will definitely use whatever BLAS and LAPACK matlab is using.

and find_optimal_rect_filter()

* Problem: integer overflow when calculating sizes (may happen e.g. with very large images)
Solution: change some types from (unsigned) long to size_t

# Conflicts:
#	dlib/dnn/tensor.h

* Fix the fact that std::numeric_limits<unsigned long>::max() isn't always the same number

* Revert serialization changes

* Review fix: use long long instead of size_t

* From long to long long all the way

* Change more types to (hopefully) make the compiler happy

* Change many more types to size_t

* Change even more types to size_t

* Minor type changes