Add jit_ellipis and remove jit_prepare argument.

* include/lightning.h, lib/jit_arm.c, lib/jit_mips.c,
	lib/jit_ppc.c, lib/jit_x86.c, lib/lightning.c: Change jit_prepare
	to no longer receive an argument. If receiving an argument, it
	should be an ABI specifier, not a boolean if varargs or not,
	and add the new jit_ellipsis call, to specify where the
	ellipsis is in the C prototype of the function being called.
	Note that currently it is not supported to define varargs
	functions and it will be ignored if calling jit_ellipsis not
	in a prepare/finish* block, but this should be addressed.

	* check/allocai.tst, check/alu_add.tst, check/alu_and.tst,
	check/alu_com.tst, check/alu_div.tst, check/alu_lsh.tst,
	check/alu_mul.tst, check/alu_neg.tst, check/alu_or.tst,
	check/alu_rem.tst, check/alu_rsh.tst, check/alu_sub.tst,
	check/alu_xor.tst, check/alux_add.tst, check/alux_sub.tst,
	check/bp.tst, check/branch.tst, check/cvt.tst, check/divi.tst,
	check/fib.tst, check/ldsti.tst, check/ldstr-c.tst,
	check/ldstr.tst, check/ldstxi-c.tst, check/ldstxi.tst,
	check/ldstxr-c.tst, check/ldstxr.tst, check/rpn.tst,
	check/lightning.c: Update for the change to jit_prepare and
	addition of jit_ellipsis.

lib/jit_mips.c

@@ -150,6 +150,12 @@ _jit_prolog(jit_state_t *_jit)
     jit_regset_new(_jit->function->regset);
 }
 
+void
+_jit_ellipsis(jit_state_t *_jit)
+{
+    _jit->function->call.kind = jit_call_varargs;
+}
+
 jit_int32_t
 _jit_allocai(jit_state_t *_jit, jit_int32_t length)
 {