Clang16 will not support implicit integers, implicit function declarations and
implicit integer to pointer conversions by default. 
This patch overhauls the source code to comply with modern C standards.

Bug: https://bugs.gentoo.org/871213
This patch was sent upstream via mail. 

Pascal Jäger <pascal.jaeger@leimstift.de> (2022-12-15)

--- a/kernel/colors.c
+++ b/kernel/colors.c
@@ -117,11 +117,7 @@ int CalcWeightsum(struct realpal_struct *realpal)
    return(0);
 }
 
-int CreateDispPal(disppal, realpal, maxcol, phongmax, rdepth, gdepth, bdepth)
-   struct disppal_struct *disppal;
-   struct realpal_struct *realpal;
-   int maxcol, rdepth, gdepth, bdepth;
-   double phongmax;
+int CreateDispPal (struct disppal_struct *disppal, struct realpal_struct *realpal, int maxcol, double phongmax, int rdepth, int gdepth, int bdepth)
 {
    int i, j, requiredcols, maxdepth, maxbright, oswcols;
    int disppos; 

--- a/kernel/files.c
+++ b/kernel/files.c
@@ -374,22 +374,7 @@ int ParseFile(const char *nam, const char *_altpath, struct keyword_struct kword
    return(0);
 }
 
-int PNGInitialization(name, mode, png, png_info, png_internal, xstart, ystart, calctime, f,
-   v, pal, realpal, colorscheme, cutbuf, zflag)
-const char *name;
-int mode;
-FILE **png;
-struct png_info_struct *png_info;
-struct png_internal_struct *png_internal;
-int xstart, ystart;
-long calctime;
-struct frac_struct *f;
-struct view_struct *v;
-struct disppal_struct *pal;
-struct realpal_struct *realpal;
-char *colorscheme;
-double *cutbuf;
-int zflag;
+int PNGInitialization (const char *name, int mode, FILE **png, struct png_info_struct *png_info, struct png_internal_struct *png_internal, int xstart, int ystart, long calctime, struct frac_struct *f, struct view_struct *v, struct disppal_struct *pal, struct realpal_struct *realpal, char *colorscheme, double *cutbuf, int zflag)
 /* rewrites file "name" */
 {
    int i, j, pos, cutpos;
--- a/kernel/quat.c
+++ b/kernel/quat.c
@@ -794,7 +794,7 @@ int CalculateFractal(char *Error, char *pngfile, FILE **png,/* struct png_info_s
       return(-1);
    }
 	   
-   my_time = (long)time((time_t)NULL);
+   my_time = (long)time((time_t*)NULL);
    if (frac.formula==0)
    { 
       cr.iterate = iterate_0; cr.iternorm = iternorm_0;
--- a/kernel/textver.c
+++ b/kernel/textver.c
@@ -143,7 +143,7 @@ int TEXTVER_putline(long x1, long x2, long xres, int y, unsigned char *Buf, int
    return(0);
 }
 
-int TEXTVER_check_event()
+int TEXTVER_check_event (void)
 {
 #ifdef __unix__
 	if (keypressed()) 
--- a/kernel/quat.c
+++ b/kernel/quat.c
@@ -949,7 +949,7 @@ int CalculateFractal(char *Error, char *pngfile, FILE **png,/* struct png_info_s
 	 { 
 	    i = view.xres*3; if (IsStereo(&view)) i *= 2;
 	    memset(line, 0, (size_t)i+1);
-	    calc_time += (long)time((time_t)NULL) - my_time;
+	    calc_time += (long)time((time_t*)NULL) - my_time;
 	    if (png != NULL)
 	    {
 	       PNGEnd(png_internal, line, 0, j);