Fix cropping when using SEncParamBase

The iFrameWidth/iFrameHeight fields are already aligned by the
SetActualPicResolution() function. Previously when iFrameWidth was
aligned directly in ParamBaseTranscode, this aligned value was used
to set iActualWidth/iActualHeight - losing the original, cropped
size.

This makes sure the output bitstream from the test of encoding
res/Static_152_100.yuv actually is cropped as it should.
Merge pull request #389 from mstorsjo/fix-cropping-param-base

Fix cropping when using SEncParamBase