Make AARCH64 harder, better, faster, stronger

- Perform some housekeeping on scalar math function code
- Import ARM's Optimized Routines for SIMD string processing
- Upgrade to latest Chromium zlib and enable more SIMD optimizations

libc/intrin/strlen.c

@@ -19,6 +19,7 @@
 #include "libc/dce.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/str/str.h"
+#ifndef __aarch64__
 
 /**
  * Returns length of NUL-terminated string.
@@ -61,3 +62,5 @@ noasan size_t strlen(const char *s) {
   return n;
 #endif
 }
+
+#endif /* __aarch64__ */