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`

examples/x86split.c

@@ -55,8 +55,8 @@ int fgethex(FILE *f) {
 }
 
 int main(int argc, char *argv[argc]) {
+  int err;
   unsigned c, i, j, l;
-  enum XedError err;
   struct XedDecodedInst xedd;
   unsigned char buf[XED_MAX_INSTRUCTION_BYTES];
   memset(buf, 0, sizeof(buf));