vec - a tiny SIMD vector header-only library written in C99

it comes with an extremely basic (and somewhat lacking) API,
where there are eight supported vector types, all 128-bit:

	vint8x16  - 16 signed 8-bit integers
	vint16x8  - 8 signed 16-bit integers
	vint32x4  - 4 signed 32-bit integers
	vint64x2  - 2 signed 64-bit integers
	vuint8x16 - 16 unsigned 8-bit integers
	vuint16x8 - 8 unsigned 16-bit integers
	vuint32x4 - 4 unsigned 32-bit integers
	vuint32x4 - 2 unsigned 64-bit integers

all of these have many operations that are prefixed with the
name of the type and an underscore, for example:

	vint8x16 vint8x16_splat(uint8_t x)
	- creates a vint8x16 where all of the values are filled
	  with the value of `x'

the current supported operations are:

	v[u]intAxB splat([u]intA_t x)
		creates a vector with all of the values are filled with
		the value of `x'

	v[u]intAxB load(const [u]intA_t x[B])
		copies the values from the memory address stored at `x';
		the address is NOT required to be aligned

	void store(v[u]intAxB vec, [u]intA_t x[B])
		copies the values from the vector into the memory address
		stored at `x'

		like with load(), this does not require address alignment

	v[u]intAxB add(v[u]intAxB vec1, v[u]intAxB vec2)
		adds the value of `vec1' and `vec2' and returns it

	v[u]intAxB sub(v[u]intAxB vec1, v[u]intAxB vec2)
		subtracts the value of `vec2' from `vec1' and returns it

	v[u]intAxB mul(v[u]intAxB vec1, v[u]intAxB vec2)
		multiplies the values of `vec1' and `vec2' together and
		returns it