Parser rejects some binary integers

The latest commit 22db720 on master rejects the following TOML document:

a = 0b1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000
b = 0b0000100010001000100010001000100010001000100010001000100010001000
c = [0b1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000]

The parser prints for example:

what(): [error] toml::parse_binary_integer:
 --> unknown file
   |
 1 | a = 0b1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000_1000
   |     ^--- too large input (> int64_t)

or a different error message if the number occurs in an array.

The value of these integers is approximately 0.533 * 2^60, easily within the range of a signed 64-bit integer.
So I believe the TOML document is valid.

The latest release v3.7.1 of toml11 parses the document correctly. However, the assignment to b invokes undefined behaviour which can be seen for example by compiling with -fsanitize=undefined.

I'm experimenting with a TOML fuzzer which revealed this issue. I guess most normal applications are not likely to hit this case, so I understand if this gets low priority. It still seems worthwhile to fix it though.

[ToruNiina]

I fixed the parse error and undefined behavior (integer overflow). Thank you!