Windows: Shift files from libnfc/windows to libnfc/contrib/win32

- Fixes the fact files were missed in package
Adds libnfc.conf.sample file to archive
Preserves error code while setting parameters

It now returns a more precise error code while using pn53x_set_property_bool() with NP_AUTO_ISO14443_4 flag.
Adds missing windows files in generated tarball
Adds nfc_free() function to freed allocated buffers

Fixes issue 228 (Thanks to Alex Lian)
Releases 1.7.0 RC5
Debian: rc4->rc5
nfc_free(): fix related doc
Debian: Fix symbols