Equivalent to C's `signed int` (`int`) type.

This type will almost always be [`i32`], but may differ on some esoteric systems. The C standard technically only requires that this type be a signed integer that is at least the size of a [`short`]; some systems define it as an [`i16`], for example.

[`short`]: type.c_short.html
[`i32`]: ../../primitive.i32.html
[`i16`]: ../../primitive.i16.html
