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/net/lunix_test.lua

@@ -70,28 +70,20 @@ function UnixTest()
    -- 1. fork off a process
    -- 2. sandbox the process
    -- 3. then violate its security
-   if GetHostOs() == "LINUX" then
-      reader, writer = assert(unix.pipe())
-      if assert(unix.fork()) == 0 then
-         assert(unix.dup(writer, 2))
-         assert(unix.pledge("stdio"))
-         unix.socket()
-         unix.exit(0)
-      end
-      unix.close(writer)
-      unix.close(reader)
-      pid, ws = assert(unix.wait())
-      assert(unix.WIFSIGNALED(ws))
-      assert(unix.WTERMSIG(ws) == unix.SIGSYS)
-   elseif GetHostOs() == "OPENBSD" then
-      if assert(unix.fork()) == 0 then
-         assert(unix.pledge("stdio"))
-         unix.socket()
-         unix.exit(1)
-      end
-      pid, ws = assert(unix.wait())
-      assert(unix.WIFSIGNALED(ws))
-      assert(unix.WTERMSIG(ws) == unix.SIGABRT)
+   if unix.pledge(nil, nil) then
+       reader, writer = assert(unix.pipe())
+       if assert(unix.fork()) == 0 then
+           assert(unix.dup(writer, 2))
+           assert(unix.pledge("stdio"))
+           unix.socket()
+           unix.exit(0)
+       end
+       unix.close(writer)
+       unix.close(reader)
+       pid, ws = assert(unix.wait())
+       assert(unix.WIFSIGNALED(ws))
+       assert(unix.WTERMSIG(ws) == unix.SIGSYS or  -- Linux
+              unix.WTERMSIG(ws) == unix.SIGABRT)   -- OpenBSD
    end
 
    -- sigaction