memset doesn't work with constants

[kdgarris]

Using a constant as the value to set with memset does not seem to work. E.g. I have a const "blank_tile" set to 32 at the beginning of my code, and when I try to use it like this:

memset screendata blank_tile 240

It produces the following assembly

`.L01636 ;; memset screendata blank_tile 240

ldy #240
lda #-1`