This patch is part of a patch series to add support for FileCheck
numeric expressions. This specific patch adds support signed numeric
values, thus allowing negative numeric values.
As such, the patch adds a new class to represent a signed or unsigned
value and add the logic for type promotion and type conversion in
numeric expression mixing signed and unsigned values. It also adds
the %d format specifier to represent signed value.
Finally, it also adds underflow and overflow detection when performing a