rapidjson

Replace RAPIDJSON_CLZLL with internal clzll (#1660)

RAPIDJSON_CLZLL is defined as macro of __builtin_clzll when
using gcc to compile. This introduces two issues:
1. in gcc __builtin_clzll returns int, not uint32_t.
2. __builtin_clzll return is undefined when input x is 0
See: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html

This patch removes RAPIDJSON_CLZLL, merges __builtin_clzll to
internal clzll with input check and return value explicit cast.

Change-Id: Iac4b355dc5e5b4ed9b3f35a640b6b5537e76f22c
Signed-off-by: Jun He <jun.he@arm.com>

Co-authored-by: Jun He <jun.he@arm.com>