Specified base_uint component size

A base_uint used to be made of an array of unsigned ints. This works
fine on most platforms, but might not work on certain present or future
platforms. The code breaks if an unsigned int is 16 or 64 bits, so it's
important to be specific. Also changed "u" to "you".
Merge pull request #2629 from wyager/master

Specified base_uint component size