python: initial impl of bindings using cFFI

A PoC that exposes single function
`enry.language_by_extension()` and a small
number of helpers to deal with string
coversion between Go<->C<->Python.

Signed-off-by: Alexander Bezzubov <bzz@apache.org>

python/enry_build.py

@@ -0,0 +1,33 @@
+from cffi import FFI
+ffibuilder = FFI()
+
+# cdef() expects a single string declaring the C types, functions and
+# globals needed to use the shared object. It must be in valid C syntax.
+ffibuilder.cdef("""
+typedef struct { const char *p; ptrdiff_t n; } _GoString_;
+typedef _GoString_ GoString;
+typedef unsigned char GoUint8;
+
+/* Return type for GetLanguageByExtension */
+struct GetLanguageByExtension_return {
+	GoString r0; /* language */
+	GoUint8 r1; /* safe */
+};
+
+extern struct GetLanguageByExtension_return GetLanguageByExtension(GoString p0);
+""")
+
+# set_source() gives the name of the python extension module to
+# produce, and some C source code as a string.  This C code needs
+# to make the declarated functions, types and globals available,
+# so it is often just the "#include".
+ffibuilder.set_source("_c_enry",
+                      """
+     #include "../.shared/libenry.h"   // the C header of the library
+""",
+                      libraries=['enry'],
+                      library_dirs=['../.shared'
+                                    ])  # library name, for the linker
+
+if __name__ == "__main__":
+    ffibuilder.compile(verbose=True)