Added special-case logical-indexing function * logical-index.h (New file) : Logical-indexing function. May be called on octave_value types via call_bool_index * nz-iterators.h : Add base-class nz_iterator for iterator types. Array has template bool for whether to internally store row-col or compute on the fly Add skip_ahead method which skips forward to the next nonzero after its argument Add flat_index for computing octave_idx_type index of current position (with assertion failure in the case of overflow) Move is_zero to separate file * ov-base-diag.cc, ov-base-mat.cc, ov-base-sparse.cc, ov-perm.cc (do_index_op): Add call to call_bool_index in logical-index.h * Array.h : Move forward-declaration for array_iterator to separate header file * dim-vector.cc (dim_max): Refers to idx-bounds.h (max_idx) * array-iter-decl.h (New file): Header file for forward declaration of array-iterator * direction.h : Add constants fdirc and bdirc to avoid having to reconstruct them * dv-utils.h, dv-utils.cc (New files) : Utility functions for querying and constructing dim-vectors * idx-bounds.h (New file) : Utility constants and functions for determining whether things will overflow the maximum allowed bounds * interp-idx.h (New function : to_flat_idx) : Converts row-col pair to linear index of octave_idx_type * is-zero.h (New file) : Function for determining whether an element is zero * logical-index.tst : Add tests for correct return-value dimensions and large sparse matrix behavior