Bug#914766: mkl: path of headers

[Mo Zhou]

Package: libmkl-dev
Version: 2019.0.117-2
Severity: important

MKL's mkl_cblas.h header can be used as a CBlas header alternative.
However when it is really used in this way, the preprocessor won't be
able to find another header "mkl_types.h" in public directory.  That
means, I'd better move the MKL headers to the public directory from the
private directory /usr/include/mkl. And this change will reduce other
software's build system maintenance burden since they won't need to add
the -I/usr/include/mkl argument anymore.

This problem is found during the local rebuild of opencv 3.2.0+dfsg-4.1 .