https://sourceforge.net/p/ttf2pt1/mailman/message/37804025/
https://bugs.gentoo.org/881321

Avoid implicit ints and implicit function declarations, and build
failures with future compilers which do not support this pre-C99
features by default.

--- a/other/bmpfont.h
+++ b/other/bmpfont.h
@@ -2,7 +2,9 @@
  * see COPYRIGHT
  */
 
+#include <stdlib.h>
 
+void
 fchkneg(file, line, rc, cmd)
 	char *file;
 	int line;
@@ -17,6 +19,7 @@ fchkneg(file, line, rc, cmd)
 	}
 }
 
+void
 fchknull(file, line, rc, cmd)
 	char *file;
 	int line;
--- a/other/cmpf.c
+++ b/other/cmpf.c
@@ -14,7 +14,7 @@
 
 #include "bmpfont.h"
 
-
+int
 main(ac, av)
 	int ac;
 	char **av;
--- a/other/dmpf.c
+++ b/other/dmpf.c
@@ -14,7 +14,7 @@
 
 #include "bmpfont.h"
 
-
+int
 main(ac, av)
 	int ac;
 	char **av;
--- a/t1asm.c
+++ b/t1asm.c
@@ -59,6 +59,8 @@ static char portnotice[] =
 #		define WINDOWS_FUNCTIONS
 #		include "windows.h"
 #	endif
+#else
+#  include <unistd.h>
 #endif
 
 /* int32 must be at least 32-bit and uint16 must be at least 16-bit */