Emit better diagnostics for out of range digits:

diag.c:1:9: error: invalid digit '8' in octal constant
int x = 000080;
        ^
diag.c:2:9: error: invalid digit 'A' in decimal constant
int z = 1000080ABC;
        ^

instead of:

diag.c:1:9: error: invalid suffix '80' on integer constant
int x = 000080;
        ^
diag.c:2:9: error: invalid suffix 'ABC' on integer constant
int z = 1000080ABC;
        ^

llvm-svn: 39605