* remove `@setGlobalAlign`
* add align keyword for setting alignment on functions and
variables.
* loads and stores use alignment from pointer
* memcpy, memset use alignment from pointer
* add syntax for pointer alignment
* slices can have volatile
* add u2, i2 primitives
* ignore preferred align and use abi align everywhere
* back to only having alignOf builtin.
preferredAlignOf is too tricky to be useful.
See #432. Partial revert of
e726925e80.
See #37