Cleanup GCC compiler attributes

Added define 'unused_' for '__attribute__((unused))'. The oldest version
of GCC with online docs (GCC 2.95.3, released in March 16, 2001 [1])
already has support for this attribute, so it doesn't make sense to
check the version.

Renamed 'noreturn' to 'noreturn_' for consistency.

[1] https://gcc.gnu.org/onlinedocs/

Signed-off-by: Antonio Niño Díaz <antonio_nd@outlook.com>

include/asm/main.h

@@ -46,7 +46,7 @@ void opt_Parse(char *s);
  * It is also used when the assembler goes into an invalid state (for example,
  * when it fails to allocate memory).
  */
-noreturn void fatalerror(const char *fmt, ...);
+noreturn_ void fatalerror(const char *fmt, ...);
 
 /*
  * Used for errors that make it impossible to assemble correctly, but don't

include/extern/err.h

@@ -34,10 +34,10 @@ void vwarn(const char *fmt, va_list ap);
 void warnx(const char *fmt, ...);
 void vwarnx(const char *fmt, va_list ap);
 
-noreturn void err(int status, const char *fmt, ...);
-noreturn void verr(int status, const char *fmt, va_list ap);
-noreturn void errx(int status, const char *fmt, ...);
-noreturn void verrx(int status, const char *fmt, va_list ap);
+noreturn_ void err(int status, const char *fmt, ...);
+noreturn_ void verr(int status, const char *fmt, va_list ap);
+noreturn_ void errx(int status, const char *fmt, ...);
+noreturn_ void verrx(int status, const char *fmt, va_list ap);
 
 #endif /* ERR_IN_LIBC */
 

include/helpers.h

@@ -11,10 +11,12 @@
 
 #ifdef __GNUC__
 	/* GCC or compatible */
-	#define noreturn __attribute__ ((noreturn))
+	#define noreturn_	__attribute__ ((noreturn))
+	#define unused_		__attribute__ ((unused))
 #else
 	/* Unsupported, but no need to throw a fit */
-	#define noreturn
+	#define noreturn_
+	#define unused_
 #endif
 
 #endif /* HELPERS_H */

include/link/script.h

@@ -13,7 +13,7 @@
 
 #include "helpers.h"
 
-noreturn void script_fatalerror(const char *fmt, ...);
+noreturn_ void script_fatalerror(const char *fmt, ...);
 
 void script_Parse(const char *path);