Fix bool for C23, which revealed an incorrect prototype.

Upstream bug: https://sourceforge.net/p/gputils/bugs/329/

--- gputils-1.5.2/libgputils/gpcoffgen.h	2017-07-09 08:56:28.000000000 +0100
+++ gputils-1.5.2/libgputils/gpcoffgen.h	2025-07-03 17:48:28.577746792 +0100
@@ -88,7 +88,7 @@
 #define RELOC_DISABLE_WARN              (1 << 0)
 #define RELOC_ENABLE_CINIT_WARN         (1 << 1)
 
-extern void gp_coffgen_check_relocations(const gp_object_t *Object, unsigned int Behavior);
+extern void gp_coffgen_check_relocations(const gp_object_t *Object, gp_boolean Enable_cinit_warns);
 
 extern gp_boolean gp_coffgen_del_reloc(gp_section_t *Section, gp_reloc_t *Relocation);
 extern const char *gp_coffgen_reloc_type_to_str(uint16_t Type);
--- gputils-1.5.2/libgputils/gptypes.h	2016-08-08 09:30:13.000000000 +0100
+++ gputils-1.5.2/libgputils/gptypes.h	2025-07-03 17:47:34.195408599 +0100
@@ -26,10 +26,7 @@
 
 #include "stdhdr.h"
 
-typedef enum {
-  false = (0 == 1),
-  true  = (0 == 0)
-} gp_boolean;
+typedef bool    gp_boolean;
 
 typedef long    gp_symvalue_t;