Now, if rate qualifiers aren't used to specify otherwise, varying
pointers point to uniform types by default. As before, uniform
pointers point to varying types by default.
float *foo; // varying pointer to uniform float
float * uniform foo; // uniform pointer to varying float
These defaults seem to require the least amount of explicit
uniform/varying qualifiers for most common cases, though TBD if it
would be easier to have a single rule that e.g. the pointed-to type
is always uniform by default.
Allow <, <=, >, >= comparisons of pointers
Allow explicit type-casting of pointers to and from integers
Fix bug in handling expressions of the form "int + ptr" ("ptr + int"
was fine).
Fix a bug in TypeCastExpr where varying -> uniform typecasts
would be allowed (leading to a crash later)
