Fix:

error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Wimplicit-int]
--- uni2ascii.c.orig	2024-06-12 10:17:17.916263000 -0700
+++ uni2ascii.c	2024-06-12 10:17:30.175434579 -0700
@@ -2679,7 +2679,7 @@
  * search may be advisable. For the time being we just do a linear search.
  */
 
-SubstituteChar(UTF32 c) {
+int SubstituteChar(UTF32 c) {
   int i;
   for(i = 0; i < SubCnt; i++) {
     if(c == SubList[i].u) {
@@ -2693,7 +2693,7 @@
   return 0;
 }
 
-AddCustomSubstitution(char *str){
+void AddCustomSubstitution(char *str){
   char *Left;
   char *Right;
   char *Delim;