move headers from include/diff/ to include/; makes things easier for consumers

repair DEBUG build

move some definitions from the public diff_main.h to an internal header file

rename 'debug.h' to 'diff_debug.h'

patience: error handling from diff_atoms_same()

add diff_atom_cmp() and error handling to diff_atom_same()

avoid include statements in header files; make each .c pull in what's needed

replace enum diff_rc errors with plain errno values

move 'struct range' and related functions into the diff_ namespace no functional change

fix wrong assignment in diff_atoms_swallow_identical_neighbors; ok neels

KNF: use max 80 columns

KNF: function declaration return types on separate line

Kill unused variables

Fix macro diff_atom_*idx return value types The macros sometimes returned unsigned int (atoms.len) or long int ((ATOM) - head). Make that always unsigned int, with some range checks against negative values.

patience: reduce sections by swallowing identical lines before LCS

initial commit