Fix -Wstringop-truncation warning.

[denravonska]

This fixes a warning I encountered when cross compiling for Raspberry Pi. If term is longer than stagingBuffer it won't be 0-terminated.

Also, fun fact. strncpy always copies the specified bytes. If the source is shorter than that it pads the rest with 0. TIL.

If the length of src is less than n, strncpy() writes additional null bytes to dest to ensure that a total of n bytes are written.

For the low end chips like AVR it could be worth adding a custom strncpy which guarantees termination without the overhead of filling the entire buffer.

char* tinygps_strncpy(char *dest, const char *src, size_t n) {
   size_t i;
   for (i = 0; i < n && src[i] != '\0'; i++)
      dest[i] = src[i];

   dest[i - 1] = 0;
   return dest;
}

[mikalhart]

Plan to fix in next release; thanks.

[denravonska]

Don't use my particular strncpy though since it goes oob if the first character is 0 :D