Won't work since the GL_LIMITS macro is defined in this way:
#define GL_LIMITS(ExtName) (GLINFO_LOCATION.max_##ExtName)
I don't think changing the variable name is an option, since keeping consistency there should be priority: ps_arb_max_local_constants -> ??? (I don't think it's wise to drop the ps_arb prefix, since it's specific to ARB and specific to PS).