Support numeric separators in C++

[matter123]

C++ supports adding single quotes between the digits of a number to form visual separation. For example, both 0x1234 and 0x1'23'4 are the same number. This extension currently only parses the number up to the first separator

Rules for what is a numeric separator:

• It cannot be the first of last character ( '0x1234 and 0x1234' )
• It cannot be after the unit specifier ( 0x'1234 )
• It cannot be next to itself ( 0x12''34 )

[mateuszchudyk]

Thank you for the issue. I'll add that feature as soon as I have a moment.