Fix cython warnings.

[jcarrano]

Description

This change fixes some C++ warnings on the file generated by Cython. Additionally, it sets the Python version to 3 in the pyx file.

Build output

Before

cythoning bfd/bfd.pyx to bfd/bfd.cpp
/home/jcarrano/source/python-bfd/.eggs/Cython-0.29-py3.7-linux-x86_64.egg/Cython/Compiler/Main.py:367: FutureWarning: Cython directive 'language_level' not set, using 2 for now (Py2). This will change in a later release! File: /home/jcarrano/source/python-bfd/bfd/bfd.pyx
  tree = Parsing.p_module(s, pxd, full_module_name)
warning: bfd/bfd.pyx:48:8: 'stdout' redeclared 
building 'bfd' extension
creating build
creating build/temp.linux-x86_64-3.7
creating build/temp.linux-x86_64-3.7/bfd
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -march=x86-64 -mtune=generic -O3 -pipe -fstack-protector-strong -fno-plt -flto=4 -fuse-linker-plugin -ffat-lto-objects -flto-partition=none -march=x86-64 -mtune=generic -O3 -pipe -fstack-protector-strong -fno-plt -march=x86-64 -mtune=generic -O3 -pipe -fstack-protector-strong -fno-plt -fPIC -DMAJOR_VERSION=1 -DMINOR_VERSION=0 -DPACKAGE=1 -DPACKAGE_VERSION=1 -I/usr/include/python3.7m -c bfd/bfd.cpp -o build/temp.linux-x86_64-3.7/bfd/bfd.o -fpermissive
bfd/bfd.cpp: In function ‘PyObject* __pyx_pf_3bfd_list_architectures(PyObject*)’:
bfd/bfd.cpp:2565:28: warning: invalid conversion from ‘const char**’ to ‘char**’ [-fpermissive]
   __pyx_v_a = bfd_arch_list();
               ~~~~~~~~~~~~~^~
bfd/bfd.cpp: In function ‘PyObject* __pyx_pf_3bfd_2list_targets(PyObject*)’:
bfd/bfd.cpp:2714:30: warning: invalid conversion from ‘const char**’ to ‘char**’ [-fpermissive]
   __pyx_v_t = bfd_target_list();
               ~~~~~~~~~~~~~~~^~
bfd/bfd.cpp: In function ‘int __pyx_pf_3bfd_3Bfd___cinit__(__pyx_obj_3bfd_Bfd*, PyObject*, PyObject*, PyObject*)’:
bfd/bfd.cpp:6534:47: warning: invalid conversion from ‘const char*’ to ‘char*’ [-fpermissive]
   __pyx_v_self->arch = bfd_printable_arch_mach(__pyx_v_self->archId, __pyx_v_self->mach);
                        ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bfd/bfd.cpp: In function ‘PyObject* __pyx_f_3bfd_3Bfd__load_sections(__pyx_obj_3bfd_Bfd*)’:
bfd/bfd.cpp:7337:46: warning: invalid conversion from ‘void*’ to ‘void (*)(bfd*, asection*, void*)’ {aka ‘void (*)(bfd*, bfd_section*, void*)’} [-fpermissive]
   bfd_map_over_sections(__pyx_v_self->abfd, ((void *)__pyx_f_3bfd_add_sections_callback), ((PyObject *)__pyx_v_self));
                                             ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from bfd/bfd.cpp:629:
/usr/include/bfd.h:1906:12: note:   initializing argument 2 of ‘void bfd_map_over_sections(bfd*, void (*)(bfd*, asection*, void*), void*)’
     void (*func) (bfd *abfd, asection *sect, void *obj),
     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bfd/bfd.cpp: In function ‘PyObject* __pyx_pf_3bfd_3Bfd_8disassemble(__pyx_obj_3bfd_Bfd*, PyObject*, PyObject*, PyObject*, PyObject*, PyObject*, PyObject*, PyObject*, PyObject*, PyObject*, PyObject*)’:
bfd/bfd.cpp:8107:23: warning: invalid conversion from ‘const bfd_target*’ to ‘bfd_target*’ [-fpermissive]
   __pyx_v_xvec_orig = __pyx_t_6;
                       ^~~~~~~~~

After

cythoning bfd/bfd.pyx to bfd/bfd.cpp
warning: bfd/bfd.pyx:49:8: 'stdout' redeclared `