Running zephir generate in Windows causes backslaskes in config.m4 files

[mlocati]

When running zephir generate under Windows, we have that paths in the config.m4 file use \ instead of /.

For example, with the RubixML/Tensor project we have these lines in the updated config.m4 file:

	AC_DEFINE(HAVE_TENSOR, 1, [Whether you have Tensor])
	tensor_sources="tensor.c kernel/main.c kernel/memory.c kernel/exception.c kernel/debug.c kernel/backtrace.c kernel/object.c kernel/array.c kernel/string.c kernel/fcall.c kernel/require.c kernel/file.c kernel/operators.c kernel/math.c kernel/concat.c kernel/variables.c kernel/filter.c kernel/iterator.c kernel/time.c kernel/exit.c tensor\arithmetic.zep.c
	tensor\arraylike.zep.c
	tensor\comparable.zep.c
	tensor\functional.zep.c
	tensor\statistical.zep.c
	tensor\trigonometric.zep.c
	tensor\tensor.zep.c
	tensor\vector.zep.c
	tensor\columnvector.zep.c
	tensor\decompositions\cholesky.zep.c
	tensor\decompositions\eigen.zep.c
	tensor\decompositions\lu.zep.c
	tensor\matrix.zep.c
	tensor\reductions\ref.zep.c
	tensor\reductions\rref.zep.c
	tensor\settings.zep.c include/indexing.c
	include/arithmetic.c
	include/comparison.c
	include/linear_algebra.c"