Make improvements

This change progresses our AARCH64 support:

- The AARCH64 build and tests are now passing
- Add 128-bit floating-point support to printf()
- Fix clone() so it initializes cosmo's x28 TLS register
- Fix TLS memory layout issue with aarch64 _Alignas vars
- Revamp microbenchmarking tools so they work on aarch64
- Make some subtle improvements to aarch64 crash reporting
- Make kisdangerous() memory checks more accurate on aarch64
- Remove sys_open() since it's not available on Linux AARCH64

This change makes general improvements to Cosmo and Redbean:

- Introduce GetHostIsa() function in Redbean
- You can now feature check using pledge(0, 0)
- You can now feature check using unveil("",0)
- Refactor some more x86-specific asm comments
- Refactor and write docs for some libm functions
- Make the mmap() API behave more similar to Linux
- Fix WIFSIGNALED() which wrongly returned true for zero
- Rename some obscure cosmo keywords from noFOO to dontFOO

libc/calls/prctl.internal.h

@@ -0,0 +1,38 @@
+#ifndef COSMOPOLITAN_LIBC_CALLS_PRCTL_INTERNAL_H_
+#define COSMOPOLITAN_LIBC_CALLS_PRCTL_INTERNAL_H_
+#include "libc/dce.h"
+#include "libc/sysv/consts/nrlinux.h"
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+forceinline int sys_prctl(int op, long a, long b, long c, long d) {
+  int rc;
+#ifdef __x86_64__
+  register long r10 asm("r10") = c;
+  register long r8 asm("r8") = d;
+  asm volatile("syscall"
+               : "=a"(rc)
+               : "0"(__NR_linux_prctl), "D"(op), "S"(a), "d"(b), "r"(r10),
+                 "r"(r8)
+               : "rcx", "r11", "memory");
+#elif defined(__aarch64__)
+  register long r0 asm("x0") = op;
+  register long r1 asm("x1") = a;
+  register long r2 asm("x2") = b;
+  register long r3 asm("x3") = c;
+  register long r4 asm("x4") = d;
+  register long res_x0 asm("x0");
+  asm volatile("mov\tx8,%1\n\t"
+               "svc\t0"
+               : "=r"(res_x0)
+               : "i"(__NR_linux_prctl), "r"(r0), "r"(r1), "r"(r2), "r"(r3),
+                 "r"(r4)
+               : "x8", "memory");
+  rc = res_x0;
+#endif
+  return rc;
+}
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_CALLS_PRCTL_INTERNAL_H_ */