Remove long-dead support for platforms without sig_atomic_t.

C89 requires <signal.h> to define sig_atomic_t, and there is no evidence
in the buildfarm that any supported platforms don't comply.  Remove the
configure test to stop wasting build cycles on a purely historical issue.
(Once upon a time, we cared about supporting C89-compliant compilers on
machines with pre-C89 system headers, but that use-case has been dead for
quite a few years.)

I have some other fixes planned in this area, but let's start with this
to see if the buildfarm produces any surprising results.

configure

@@ -14151,20 +14151,6 @@ _ACEOF
 fi
 
 
-# We also check for sig_atomic_t, which *should* be defined per ANSI
-# C, but is missing on some old platforms.
-ac_fn_c_check_type "$LINENO" "sig_atomic_t" "ac_cv_type_sig_atomic_t" "#include <signal.h>
-"
-if test "x$ac_cv_type_sig_atomic_t" = xyes; then :
-
-cat >>confdefs.h <<_ACEOF
-#define HAVE_SIG_ATOMIC_T 1
-_ACEOF
-
-
-fi
-
-
 # Check for extensions offering the integer scalar type __int128.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for __int128" >&5
 $as_echo_n "checking for __int128... " >&6; }

configure.in

@@ -1831,10 +1831,6 @@ AC_DEFINE_UNQUOTED(MAXIMUM_ALIGNOF, $MAX_ALIGNOF, [Define as the maximum alignme
 AC_CHECK_TYPES([int8, uint8, int64, uint64], [], [],
 [#include <stdio.h>])
 
-# We also check for sig_atomic_t, which *should* be defined per ANSI
-# C, but is missing on some old platforms.
-AC_CHECK_TYPES(sig_atomic_t, [], [], [#include <signal.h>])
-
 # Check for extensions offering the integer scalar type __int128.
 PGAC_TYPE_128BIT_INT
 

src/include/c.h

@@ -334,11 +334,6 @@ typedef unsigned PG_INT128_TYPE uint128;
 #define HAVE_INT64_TIMESTAMP
 #endif
 
-/* sig_atomic_t is required by ANSI C, but may be missing on old platforms */
-#ifndef HAVE_SIG_ATOMIC_T
-typedef int sig_atomic_t;
-#endif
-
 /*
  * Size
  *		Size of any memory resident object, as returned by sizeof.

src/include/pg_config.h.in

@@ -449,9 +449,6 @@
 /* Define to 1 if you have sigsetjmp(). */
 #undef HAVE_SIGSETJMP
 
-/* Define to 1 if the system has the type `sig_atomic_t'. */
-#undef HAVE_SIG_ATOMIC_T
-
 /* Define to 1 if you have the `snprintf' function. */
 #undef HAVE_SNPRINTF
 

src/include/pg_config.h.win32

@@ -322,9 +322,6 @@
 /* Define to 1 if you have sigsetjmp(). */
 /* #undef HAVE_SIGSETJMP */
 
-/* Define to 1 if the system has the type `sig_atomic_t'. */
-#define HAVE_SIG_ATOMIC_T 1
-
 /* Define to 1 if you have the `snprintf' function. */
 /* #undef HAVE_SNPRINTF */