Convert the the USB device name UTF8

The USB device name is a UTF16 string but the `spndev.name` is a `char *`.
This causes confusion when someone tries to `printf` the device name and
gets only the first character, because the second byte is 0.

To avoid this convert the device name to UTF8. For devices whose names are
ASCII (most cases) this will result in a plain ASCIIZ string and avoid
confusion.

At the same time the driver API remains "simple" for embedded platforms
where the USB HID implementation will not be HIDAPI and Unicode support
may be missing (or too large to compile in).

Fixes #6

Author: ruevs

src/usbdev.c

@@ -145,14 +145,21 @@ int spndev_usb_open(struct spndev *dev, const char *devstr, uint16_t vend, uint1
                     pidmatch = 1;
                     hid_device* hiddev = hid_open_path(cinfo->path);
                     if (hiddev) {
+                        size_t name_length;
+
                         if (!(dev->path = _strdup(cinfo->path))) {
                             fprintf(stderr, "spndev_open: Failed to allocate device path\n");
                             goto cleanup;
                         }
-                        if (!(dev->name = (char*)_wcsdup(cinfo->product_string))) {
+
+                        // The length of the UTF8 encoding of the UTF16 device name + 1 fot the 0
+                        name_length = 1 + wcsrtombs(0, &cinfo->product_string, 0, 0);
+                        if (!(dev->name = (char*)calloc(1, name_length))) {
                             fprintf(stderr, "spndev_open: Failed to allocate device name\n");
                             goto cleanup;
                         }
+                        name_length = wcsrtombs(dev->name, &cinfo->product_string, name_length, 0);
+
                         if (-1 == hid_set_nonblocking(hiddev, 1)) {
                             fprintf(stderr, "spndev_open: Failed to set non-blocking HID mode.\n");
                             goto cleanup;