Make AttributeUtil.split() ignore trailing space.
Make AttributeUtil.split() ignore trailing space.

This fixes a problem that was reported by Jason Kiss (thanks!) in checking
of aria-controls and aria-labelledby values with trailing whitespace.

tripu/validator,sammuelyee/validator,validator/validator,sammuelyee/validator,tripu/validator,validator/validator,sammuelyee/validator,YOTOV-LIMITED/validator,takenspc/validator,validator/validator,tripu/validator,takenspc/validator,takenspc/validator,YOTOV-LIMITED/validator,sammuelyee/validator,YOTOV-LIMITED/validator,YOTOV-LIMITED/validator,tripu/validator,takenspc/validator,tripu/validator,validator/validator,YOTOV-LIMITED/validator,sammuelyee/validator,takenspc/validator,validator/validator