Build tweaks for ancient Macs

I don't expect anyone else to actually use ksh93 on a museum-grade
Power Mac G5 running Mac OS X 10.3.7, but ancient platforms are
great bug and compatibility testing tools. These tweaks restore the
ability to build on that platform.

Also, to avoid a strange path search bug on that platform and
possibly other ancient ones, set SHOPT_DYNAMIC to 0 in SHOPT.sh.

src/cmd/builtin/pty.c

@@ -257,7 +257,12 @@ mkpty(int* master, int* minion)
 	tty.c_lflag |= ECHOKE;
 #endif
 	tty.c_oflag |= (ONLCR | OPOST);
-	tty.c_oflag &= ~(OCRNL | ONLRET);
+#ifdef OCRNL
+	tty.c_oflag &= ~OCRNL;
+#endif
+#ifdef ONLRET
+	tty.c_oflag &= ~ONLRET;
+#endif
 	tty.c_iflag |= BRKINT;
 	tty.c_iflag &= ~IGNBRK;
 	tty.c_cc[VTIME] = 0;

src/cmd/ksh93/sh/xec.c

@@ -52,6 +52,10 @@
 #   define vfork()      fork()
 #endif
 
+#if _lib_getrusage && !defined(RUSAGE_SELF)
+#   include <sys/resource.h>
+#endif
+
 #define SH_NTFORK	SH_TIMING
 #define NV_BLTPFSH	NV_ARRAY
 

src/lib/libast/misc/debug.c

@@ -37,9 +37,12 @@ debug_fatal(const char* file, int line)
 	abort();
 }
 
-#if defined(_sys_times) && defined(_lib_getrusage)
+#if _sys_times && _lib_getrusage
 
 #include <times.h>
+#ifndef RUSAGE_SELF
+#include <sys/resource.h>
+#endif
 double
 debug_elapsed(int set)
 {