16 digit Hexadecimals

[chrimbo]

Environment

toml++ version and/or commit hash:
toml++ v3.4.0

**Compiler: **
MinGW81_64, GCC 8.1.0

C++ standard mode:
c++17

Target arch:
x86_64

Describe the bug

I'm trying to parse Value=0xca343183acdf73b4 , resulting in an "Error while parsing hexadecimal integer: '0xca343183acdf73b4' is not representable in 64 bits "

Also tried Value=-0x35CBCE7C53208C4C , resulting in "Error while parsing hexadecimal interger: expected '0', saw '-'"

and
Value=0x-35CBCE7C53208C4C, also resulting in "Error while parsing hexadecimal integer: expected digit, saw '-'"