BuildSystem: Avoid obsolete warning with AC_TYPE_SIGNAL on autoconf.

Removed the obsolete macro AC_TYPE_SIGNAL because Asterisk does not use K&R C
but requires ANSI C anyway.

ASTERISK-26046

Change-Id: I914c014385e1862102d90fe7650621def78db02e

configure

@@ -13987,39 +13987,6 @@ _ACEOF
 
 rm -f conftest*
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking return type of signal handlers" >&5
-$as_echo_n "checking return type of signal handlers... " >&6; }
-if ${ac_cv_type_signal+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-#include <sys/types.h>
-#include <signal.h>
-
-int
-main ()
-{
-return *(signal (0, 0)) (0) == 1;
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_compile "$LINENO"; then :
-  ac_cv_type_signal=int
-else
-  ac_cv_type_signal=void
-fi
-rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_type_signal" >&5
-$as_echo "$ac_cv_type_signal" >&6; }
-
-cat >>confdefs.h <<_ACEOF
-#define RETSIGTYPE $ac_cv_type_signal
-_ACEOF
-
-
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether lstat correctly handles trailing slash" >&5
 $as_echo_n "checking whether lstat correctly handles trailing slash... " >&6; }
 if ${ac_cv_func_lstat_dereferences_slashed_symlink+:} false; then :

configure.ac

@@ -588,7 +588,6 @@ AC_PROG_GCC_TRADITIONAL
 AC_FUNC_MEMCMP
 AC_FUNC_MMAP
 AC_FUNC_SELECT_ARGTYPES
-AC_TYPE_SIGNAL
 AC_FUNC_STAT
 AC_FUNC_STRCOLL
 AC_FUNC_STRFTIME

include/asterisk/autoconfig.h.in

@@ -1185,9 +1185,6 @@
 /* Define if your system needs braces around PTHREAD_ONCE_INIT */
 #undef PTHREAD_ONCE_INIT_NEEDS_BRACES
 
-/* Define as the return type of signal handlers (`int' or `void'). */
-#undef RETSIGTYPE
-
 /* Define to the type of arg 1 for `select'. */
 #undef SELECT_TYPE_ARG1