Fix problems in relation to Fedora's C99 instrumentation (#665)

This commit applies the necessary changes to the ksh codebase to
fix C99 compilation when using Red Hat's instrumented GCC[*],
though note that a patch to redhat-rpm-config is also required and
must be applied separately[*2].

[*1] https://fedoraproject.org/wiki/Toolchain/PortingToModernC
[*2] #664 (comment)

src/lib/libast/comp/conf.tab:
- Add include directives to fix implicit function declarations that
  cause the PID_MAX test to silently fail. This compile error
  occurs on all platforms when compiling with strict C99, but
  wasn't exposed even after setting IFFEFLAGS to -d1 or -d2 (that's
  likely a separate bug in conf.sh that'll need fixing). As a
  consequence, it could cause following bug in the getconf builtin
  (now fixed as of this commit):
    $ /opt/ast/bin/getconf PID_MAX
    30000  # Wrong, should be the platform value (e.g., 4194304)

src/lib/libast/{features/lib,sfio/sfhdr.h}:
- Delete the lib_poll_fd_2 feature test and associated code, which
  allowed ksh to used non-compliant implementations of poll(3).
  This feature test fails on POSIX-compliant systems with
  int-conversion errors, which is the expected result. However, the
  C99 instrumentation used by Red Hat marks the entire build as a
  failure because of the fact those errors exist at all, even
  though the build proceeds as normal. Fortunately, the operating
  systems supported by ksh (AFAIK) all have proper, POSIX-compliant
  versions of poll() and thus don't need this test. To work around
  the flawed instrumentation, the unnecessary test has been
  jettisoned.

NEWS

@@ -7,6 +7,9 @@ Uppercase BUG_* IDs are shell bug IDs as used by the Modernish shell library.
 - Fixed incorrect rejection of the tab key while reading input using the `read`
   built-in command. Bugs introduced on 2021-02-26 (emacs) and 2022-08-24 (vi).
 
+- Fixed a minor bug that could cause '/opt/ast/bin/getconf PID_MAX' to
+  return the wrong value when ksh is built with strict C99.
+
 2023-06-13:
 
 - Fixed a serious regression in pathname expansion where quoted wildcard

src/lib/libast/comp/conf.tab

@@ -390,6 +390,9 @@ PBS_MESSAGE			POSIX	SC 2 FUW
 PBS_TRACK			POSIX	SC 2 FUW
 PHYS_PAGES			SUN	SC 1 0
 PID_MAX				SVID	SC 1 LMU	30000	cc{
+	#include <fcntl.h>
+	#include <stdio.h>
+	#include <stdlib.h>
 	int main(void)
 	{
 		long	v;

src/lib/libast/features/lib

@@ -68,7 +68,7 @@ tst	tst_errno note{ errno can be assigned }end link{
 	int main(void) { errno = 0; error(); strerror(); return 0; }
 }end
 
-tst	lib_poll_fd_1 note{ fd is first arg to poll() }end execute{
+tst	lib_poll note{ poll() args comply with the POSIX standard }end execute{
 	#include <poll.h>
 	#include <unistd.h>
 	extern int	pipe(int*);
@@ -87,28 +87,6 @@ tst	lib_poll_fd_1 note{ fd is first arg to poll() }end execute{
 	}
 }end
 
-tst	lib_poll_fd_2 note{ fd is second arg to poll() }end execute{
-	#include <poll.h>
-	#include <unistd.h>
-	extern int	pipe(int*);
-	int
-	main(void)
-	{	int		rw[2];
-		struct pollfd	fd;
-		if (pipe(rw) < 0) return 1;
-		fd.fd = rw[0];
-		fd.events = POLLIN;
-		fd.revents = 0;
-		return poll(1, &fd, 0) < 0;
-		if (poll(1, &fd, 0) < 0 || fd.revents != 0) return 1;
-		if (write(rw[1], "x", 1) != 1) return 1;
-		if (poll(1, &fd, 0) < 0 || fd.revents == 0) return 1;
-		return 0;
-	}
-}end
-
-exp	_lib_poll	_lib_poll_fd_1||_lib_poll_fd_2
-
 tst	lib_poll_notimer note{ poll with no fds ignores timeout }end execute{
 	#include <sys/types.h>
 	#include <poll.h>

src/lib/libast/sfio/sfhdr.h

@@ -103,21 +103,12 @@
 #if _sys_select
 #include	<sys/select.h>
 #endif
-#else
-#if _lib_poll_fd_1 || _lib_poll_fd_2
-#define _lib_poll	1
-#endif
 #endif /*_lib_select_*/
 
 #if _lib_poll
 #include	<poll.h>
-
-#if _lib_poll_fd_1
 #define SFPOLL(pfd,n,tm)	poll((pfd),(ulong)(n),(tm))
-#else
-#define SFPOLL(pfd,n,tm)	poll((ulong)(n),(pfd),(tm))
 #endif
-#endif /*_lib_poll*/
 
 #if _stream_peek
 #include	<stropts.h>