[lex.ppnumber]
Change: pp-number can contain one or more single quotes.
Rationale: Necessary to enable single quotes as digit separators.
Effect on original feature: Valid C++ 2011 code may fail to compile or may change meaning in this
International Standard. For example, the following code is valid both in C++ 2011 and in
this International Standard, but the macro invocation produces different outcomes
because the single quotes delimit a character literal in C++ 2011, whereas they are digit
separators in this International Standard:
#define M(x, ...) __VA_ARGS__
int x[2] = { M(1'2,3'4) };
// int x[2] = {}; — C++ 2011
// int x[2] = { 3'4 }; — this International Standard