Fix an infinite loop on archs where char is unsigned by default (arm*
and powerpc), because EOF (-1) could not be reached by getc(3).

Index: unireverse.c
--- unireverse.c.orig
+++ unireverse.c
@@ -151,7 +151,7 @@ int main(int ac, char **av) {
 
 char * GetLine(FILE *fp, int *LineLength)
 {
-  char c;
+  int c;
   int Available;
   int CharsRead;
   char *Line;