The two functions that are assigned to the formulas structs secnod field
`int (*calculate)(number_t number_t number_t number_t)`
(without the REGISTERS(3) which is just a macro to GCC regparm)

However, clang16 has -Wincompatible-function-pointer-types by default, and it
does not like that and complains, that assigning these functions into the
structs fields is a problem due to incompatible types. 

Bug: https://bugs.gentoo.org/880385

Signed-off-by: Pascal Jäger <pascal.jaeger@leimstift.de>

--- a/formulas.h
+++ b/formulas.h
@@ -50,7 +50,7 @@ struct symetryinfo {
 #define FORMULAMAGIC 1121
 struct formula {
     int magic;
-    int (*calculate) (number_t, number_t, number_t, number_t) REGISTERS(3);
+    int (*calculate) (number_t, number_t, number_t, number_t);
     char *name[2];
     vinfo v;
     int mandelbrot;