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

tool/emacs/c.lang

@@ -88,7 +88,7 @@ Keywords={
 "textexit",
 "externinline",
 "dontinline",
-"noclone",
+"dontclone",
 "donothing",
 "printfesque",
 "flattenout",
@@ -102,7 +102,7 @@ Keywords={
 "forceinline",
 "nocallersavedregisters",
 "dontthrow",
-"nooptimize",
+"dontoptimize",
 "optimizesize",
 "optimizespeed",
 "alignof",