Major redesign of function call handling.

Drop call gates. Use function headers, dispatched like bytecodes.
Emit BC_FUNCF/BC_FUNCV bytecode at PC 0 for all Lua functions.
C functions and ASM fast functions get extra bytecodes.
Modify internal calling convention: new base in BASE (formerly in RA).
Can now use better C function wrapper semantics (dynamic on/off).
Prerequisite for call hooks with zero-overhead if disabled.
Prerequisite for compiling recursive calls.
Prerequisite for efficient 32/64 bit prototype guards.

src/lj_bc.c

@@ -9,11 +9,6 @@
 #include "lj_obj.h"
 #include "lj_bc.h"
 
-/* Bytecode instruction modes. */
-LJ_DATADEF const uint16_t lj_bc_mode[BC__MAX+1] = {
-BCDEF(BCMODE)
-  0
-};
-
+/* Bytecode offsets and bytecode instruction modes. */
 #include "lj_bcdef.h"