Update .gitignore.

* OpenCV4Tegra/ is no longer relevant.
* We should only ignore the particular refman.rst that we generate.
Sorted .gitignore.
Revert "disable SVM when AMD BLAS is not available"

This reverts commit d63a38e9bfad4081ec8107e8d38e03c03f6548d2.

Conflicts:
	modules/ocl/test/test_ml.cpp
ocl: svm: restore non BLAS version
fixed ocl::copyMakeBorder accuracy test
Merge pull request #1749 from SpecLad:update-ignore
ocl: memory cleanup workaround: clFinish() before clReleaseMemObject() + 64kb memory guard
Merge pull request #1745 from alalek:ocl_fix_svm_with_blas
Merge pull request #1751 from ilya-lavrenov:ocl_copyMakeBorder_test_fix
Merge pull request #1752 from alalek:ocl_memory_cleanup_workaround