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

test/libc/intrin/kprintf_test.c

@@ -221,14 +221,13 @@ TEST(ksnprintf, testSymbols) {
   }
 }
 
-#ifdef __x86_64__
 TEST(ksnprintf, fuzzTheUnbreakable) {
   int e;
   size_t i;
   uint64_t x;
   char *f, b[32];
   _Alignas(FRAMESIZE) static const char weasel[FRAMESIZE];
-  asm("mov\t%1,%0" : "=r"(f) : "g"(weasel));
+  f = VEIL("r", weasel);
   EXPECT_SYS(0, 0, mprotect(f, FRAMESIZE, PROT_READ | PROT_WRITE));
   strcpy(f, "hello %s\n");
   EXPECT_EQ(12, ksnprintf(b, sizeof(b), f, "world"));
@@ -243,7 +242,6 @@ TEST(ksnprintf, fuzzTheUnbreakable) {
   }
   EXPECT_SYS(0, 0, mprotect(f, FRAMESIZE, PROT_READ));
 }
-#endif /* __x86_64__ */
 
 TEST(kprintf, testFailure_wontClobberErrnoAndBypassesSystemCallSupport) {
   int n;