Improve signals and memory protection

- Document sigaction()
- Simplify New Technology fork() code
- Testing and many bug fixes for mprotect()
- Distribute Intel Xed ILD in the amalgamation
- Turn Xed enums into defines to avoid DWARF bloat
- Improve polyfilling of SA_SIGINFO on BSDs and fix bugs
- setpgid(getpid(), getpid()) on Windows will ignore CTRL-C
- Work around issues relating to NT mappings being executable
- Permit automatic executable stack override via `ape_stack_pf`

libc/calls/struct/siginfo-netbsd.internal.h

@@ -0,0 +1,53 @@
+#ifndef COSMOPOLITAN_LIBC_CALLS_STRUCT_SIGINFO_NETBSD_H_
+#define COSMOPOLITAN_LIBC_CALLS_STRUCT_SIGINFO_NETBSD_H_
+#include "libc/calls/struct/sigval.h"
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+struct siginfo_netbsd {
+  int32_t si_signo;
+  int32_t si_code;
+  int32_t si_errno;
+  int32_t __pad;
+  union {
+    struct { /* RT */
+      int32_t si_pid;
+      int32_t si_uid;
+      union sigval si_value;
+    };
+    struct { /* chld */
+      int32_t _pid;
+      int32_t _uid;
+      int32_t si_status;
+      int64_t si_utime;
+      int64_t si_stime;
+    };
+    struct { /* fault */
+      void *si_addr;
+      int32_t si_trap;
+      int32_t si_trap2;
+      int32_t si_trap3;
+    };
+    struct { /* poll */
+      int64_t si_band;
+      int32_t si_fd;
+    };
+    struct { /* syscall */
+      int32_t si_sysnum;
+      int32_t si_retval[2];
+      int32_t si_error;
+      uint64_t si_args[8];
+    };
+    struct { /* ptrace */
+      int32_t si_pe_report_event;
+      union {
+        int32_t si_pe_other_pid;
+        int32_t si_pe_lwp;
+      };
+    };
+  };
+};
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_CALLS_STRUCT_SIGINFO_NETBSD_H_ */