* Add utility functions, improve integer conversion functions
- move `is_be()` to cutils.h
- add `is_upper_ascii()` and `to_upper_ascii()`
- add extensive benchmark for integer conversion variants in **tests/test_conv.c**
- add `u32toa()`, `i32toa()`, `u64toa()`, `i64toa()` based on register shift variant
- add `u32toa_radix()`, `u64toa_radix()`, `i64toa_radix()` based on length_loop variant
- use direct converters instead of `snprintf()`
- copy NaN and Infinity directly in `js_dtoa1()`
- optimize `js_number_toString()` for small integers
- use `JS_NewStringLen()` instead of `JS_NewString()` when possible
- add more precise conversion tests in microbench.js
- disable some benchmark tests for gcc (they cause ASAN failures)
Add REOP_char8 that matches single bytes. Compresses bytecode for the
ASCII common case by 33% and reduces regexp_ascii benchmark running time
by 4%. The regexp_utf16 benchmark is unaffected.
The removal of the high-precision but non-standard clock source in
commit 5af98ca broke microbench because Date.now() is not granular
enough for the benchmark runner to make forward progress.
This commit adds a new method to the os module that returns time
with microsecond precision.
