ignore more artifacts generated during build

[defnvary]

Description

This adds following files to .gitignore

src/borg/hashindex.c
src/borg/platform/netbsd.c

[ThomasWaldmann]

I did a check only on master branch. The files in the list below are generated from .pyx files and should be gitignored. But: ./src/borg/_item.c must not be gitignored.

./src/borg/hashindex.c
./src/borg/crypto/low_level.c
./src/borg/compress.c
./src/borg/chunkers/reader.c
./src/borg/chunkers/buzhash.c
./src/borg/chunkers/buzhash64.c
./src/borg/platform/freebsd.c
./src/borg/platform/posix.c
./src/borg/platform/syncfilerange.c
./src/borg/platform/darwin.c
./src/borg/platform/netbsd.c
./src/borg/platform/linux.c
./src/borg/platform/windows.c
./src/borg/item.c
./src/borg/checksums.c

[defnvary]

I did a check only on master branch. The files in the list below are generated from .pyx files and should be gitignored. But: ./src/borg/_item.c must not be gitignored.

./src/borg/hashindex.c
./src/borg/crypto/low_level.c
./src/borg/compress.c
./src/borg/chunkers/reader.c
./src/borg/chunkers/buzhash.c
./src/borg/chunkers/buzhash64.c
./src/borg/platform/freebsd.c
./src/borg/platform/posix.c
./src/borg/platform/syncfilerange.c
./src/borg/platform/darwin.c
./src/borg/platform/netbsd.c
./src/borg/platform/linux.c
./src/borg/platform/windows.c
./src/borg/item.c
./src/borg/checksums.c

All these are already ignored.

[ThomasWaldmann]

Thanks!