Add varargs freeMatrices(), multiplyMatrices().

Add:
	src/matrix.c
		-add freeMatrices() and multiplyMatrices(), which accepts varargs
		Matrix_t *s and call freeMatrix() and multiplyMatrix() on the arguments
		accordingly.
Add static specifiers to matrix, utils functions.

Add:
	src/(matrix, utils).c
		-add static specifiers to functions that each file used only internally
		(eg, dotProduct() and sig_handler).
Merge branch 'varargs_functions'

Conflicts:
	src/matrix.h