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`

tool/decode/x86opinfo.c

@@ -38,7 +38,7 @@ const struct IdName kXedModeNames[] = {
     {XED_MACHINE_MODE_UNREAL, "unreal"},
 };
 
-enum XedMachineMode g_mode;
+int g_mode;
 struct XedDecodedInst g_xedd;
 
 wontreturn void ShowUsage(int rc, FILE *f) {