refactor --for BaseEncoderTest
Make sure the width/height is large enough in SetOptionEncParamExt

When using 4 downsampled layers, make sure the random width/height
is large enough that the downsampled layers don't have a zero size.

Since the value never will be too small now, there's no need to
use WELS_CLIP3 any longer.
Avoid warnings about converting from int to bool

MSVC used to warn about this.
Add a cast when converting from int64_t to float

This avoids a warning when building with MSVC.
add validation of slice parameters instead of assert
Merge pull request #1472 from mstorsjo/fix-test-random

Make sure the width/height is large enough in SetOptionEncParamExt
Merge pull request #1478 from sijchen/after_review61

[Encoder] add validation of slice parameters instead of assert
Merge pull request #1477 from mstorsjo/avoid-msvc-warnings

Avoid warnings when building with MSVC
Set constraint set 0 and 1 flags for non-scalable as well

This allows decoders to know that a baseline stream doesn't
contain any of the features that aren't in the constrained
baseline subset.

Set the flags based on what profile we target.
Merge pull request #1476 from mstorsjo/sps-constraints

Set constraint set 0 and 1 flags for non-scalable as well
Merge pull request #1469 from shihuade/APIUTV1.5.2

refactor --for BaseEncoderTest
Merge remote-tracking branch 'upstream/master' into travis.osx