Improve organization of CFFI setup

.gitignore

@@ -14,7 +14,7 @@ venv-3.5/
 */test/output
 bin/
 include/
-lib/
+ocrmypdf/lib/_*.py
 pip-selfcheck.json
 pyvenv.cfg
 htmlcov/
@@ -23,4 +23,5 @@ htmlcov/
 .ipynb_checkpoints/
 tests/cache/
 tests/resources/private
-ocrmypdf/version.py
+ocrmypdf/version.py
+.eggs/

ocrmypdf/leptonica.py

@@ -15,7 +15,7 @@ import os
 import logging
 from tempfile import TemporaryFile
 from ctypes.util import find_library
-from ._leptonica import ffi
+from .lib._leptonica import ffi
 
 lept = ffi.dlopen(find_library('lept'))
 

ocrmypdf/lib/compile_leptonica.py

@@ -1,7 +1,7 @@
 from cffi import FFI
 
 ffi = FFI()
-ffi.set_source("_leptonica", None)
+ffi.set_source("ocrmypdf.lib._leptonica", None)
 ffi.cdef("""
 typedef signed char             l_int8;
 typedef unsigned char           l_uint8;

setup.py

@@ -206,9 +206,13 @@ setup(
         "Topic :: Text Processing :: Linguistic",
         ],
     setup_requires=[
-        'setuptools_scm'
+        'setuptools_scm',
+        'cffi>=1.0.0'
     ],
     use_scm_version={'version_scheme': 'post-release'},
+    cffi_modules=[
+        'ocrmypdf/lib/compile_leptonica.py:ffi'
+    ],
     install_requires=[
         'ruffus',
         'Pillow',