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/plinko/test.mk

@@ -1,6 +1,8 @@
 #-*-mode:makefile-gmake;indent-tabs-mode:t;tab-width:8;coding:utf-8-*-┐
 #───vi: set et ft=make ts=8 tw=8 fenc=utf-8 :vi───────────────────────┘
 
+ifeq ($(ARCH), x86_64)
+
 PKGS += TEST_TOOL_PLINKO
 
 TEST_TOOL_PLINKO = $(TOOL_PLINKO_A_DEPS) $(TOOL_PLINKO_A)
@@ -86,3 +88,8 @@ o/$(MODE)/test/tool/plinko/library_test.lisp.zip.o: private ZIPOBJ_FLAGS += -B
 o/$(MODE)/test/tool/plinko:					\
 		$(TEST_TOOL_PLINKO_BINS)			\
 		$(TEST_TOOL_PLINKO_CHECKS)
+
+else
+.PHONY: o/$(MODE)/test/tool/plinko
+o/$(MODE)/test/tool/plinko:
+endif