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/strcmp_test.c

@@ -108,8 +108,8 @@ TEST(strncmp, testInequality) {
   char *s1 = strcpy(malloc(2), "1");
   char *s2 = strcpy(malloc(1), "");
   ASSERT_EQ(0, strncmp(s1, s2, 0));
-  ASSERT_EQ('1', strncmp(s1, s2, 1));
-  ASSERT_EQ(-'1', strncmp(s2, s1, 1));
+  ASSERT_GT(strncmp(s1, s2, 1), 0);
+  ASSERT_LT(strncmp(s2, s1, 1), 0);
   free(s2);
   free(s1);
 }