Straightforward (naive) implementation of bicubic interpolation
Add bicubic interpolation to interp2d.h
Add bicubic.c to files built
Add array brackets to bicubic_inversion_matrix declaration
Add one test of bicubic interpolation
Initialize z_accumulator in bicubic interpolator
Change return type of test function
Merge branch 'master' of github.com:diazona/interp2d into bicubic

Conflicts:
	test.c
Add GPL notice at top of file
Add in bicubic interpolation code
Merge branch 'master' into bicubic
Enhance tests of bicubic interpolation
Merge branch 'bicubic'

Conflicts:
	CMakeLists.txt
	test.c