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/tool/build/lib/divmul_test.c

@@ -16,6 +16,7 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "tool/build/lib/divmul.h"
 #include "libc/calls/struct/sigaction.h"
 #include "libc/macros.internal.h"
 #include "libc/runtime/runtime.h"
@@ -25,10 +26,10 @@
 #include "libc/testlib/testlib.h"
 #include "libc/x/xsigaction.h"
 #include "third_party/xed/x86.h"
-#include "tool/build/lib/divmul.h"
 #include "tool/build/lib/endian.h"
 #include "tool/build/lib/flags.h"
 #include "tool/build/lib/machine.h"
+#ifdef __x86_64__
 
 #define CX     1
 #define OSZ    00000000040
@@ -551,3 +552,5 @@ TEST(div64, test) {
     }
   }
 }
+
+#endif /* __x86_64__ */