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

libc/macros.internal.h

@@ -170,6 +170,31 @@
 	.previous
 .endm
 
+//	Begins definition of frameless function that calls no functions.
+.macro	.leafprologue
+#if !(defined(TINY) && !defined(__PG__))
+#ifdef __x86_64__
+	push	%rbp
+	mov	%rsp,%rbp
+#elif defined(__aarch64__)
+	stp	x29,x30,[sp,#-16]!
+	mov	x29,sp
+#endif
+#endif
+.endm
+
+//	Ends definition of frameless function that calls no functions.
+.macro	.leafepilogue
+#if !(defined(TINY) && !defined(__PG__))
+#ifdef __x86_64__
+	pop	%rbp
+#elif defined(__aarch64__)
+	ldp	x29,x30,[sp],#16
+#endif
+#endif
+	ret
+.endm
+
 //	Documents unreachable assembly code.
 .macro	.unreachable
 #if !defined(NDEBUG) && defined(__x86_64__)
@@ -390,22 +415,6 @@
 	.byte	0x0f,0x1f,0105,\endfunc-.	# nopl disp8(%rbp)
 .endm
 
-//	Begins definition of frameless function that calls no functions.
-.macro	.leafprologue
-#if !(defined(TINY) && !defined(__PG__))
-	push	%rbp
-	mov	%rsp,%rbp
-#endif
-.endm
-
-//	Ends definition of frameless function that calls no functions.
-.macro	.leafepilogue
-#if !(defined(TINY) && !defined(__PG__))
-	pop	%rbp
-#endif
-	ret
-.endm
-
 //	Good alignment for functions where alignment actually helps.
 //	@note 16-byte
 .macro	.alignfunc