The v6 and v6p targets don't have horizontal operations, instead they
have direct vector/quaternion equality to float/int scalar result. Fixes
an ice when building game-source/quake.
Because the glsl front-end uses Ruamoko to compile its builtins, it
needs to switch languages, and the cleanest way to do so is to use a
context object that gets passed around. This removes not only the
current_language global, but also (as a bonus) any real references to
flex's scanner object (there's still a pointer in rua_ctx_t, but it's no
longer a parameter (which caused some pain in the change)).
The main goal was to make it possible to give generic functions
definitions (since the code would be very dependent on the actual
parameter types), but will also allow for inline functions. It also
helped move a lot of the back-end dependent code out of semantics
processing and almost completely (if not completely) out of the parser.
Possibly more importantly, it gets the dags flushing out of the parser,
which means such is now shared by all front-ends.
There's probably a lot of dead code in expr.c now, but that can be taken
care of another time.
Ruamoko and v6(p) have their own copies despite being (currently) the
same, and spir-v's is currently empty, but now targeting spir-v doesn't
try to emit ruamoko code.
I'd gotten tired of all the convoluted progs version checks, and with
the addition of spirv, they're not even always relevant, and adding C
(when I get to it) will make things even worse. However, for now the
first victim is just the parameter/return value size check.
