To conclude, if someone encounters the same question as mine , just try an old version of devkitARM, and everything will be fine.
This is what worked for me (well, the analogous thing, in a different source setup):
@ at top
.equ MEANINGFUL_NAME, 0x08054678 - CSAPS_CORRECT
@ later on
bl MEANINGFUL_NAME
Notice there is no .org use here. My notes are quite disorganized, but it appears that my original install of devkitARM is version 32. (That was on a previous computer, and I’ve been getting by recently by just copying around the as.exe and objcopy.exe where I need them… 
)