Tint changes during Origin Trial

Changes for M97

Deprecated modf() and frexp() builtin overloads that take a pointer second parameter have been removed.

The size of an array can now be defined using a non-overridable module-scope constant
The num_workgroups builtin is now supported.

Hex floats: now correctly errors when the magnitude is non-zero, and the exponent would cause overflow. tint:1150, tint:1166
Identifiers beginning with an underscore are now correctly rejected. tint:1179
abs() fixed for unsigned integers on SPIR-V backend tint:1179