Use strcmp() instead of strncmp() when comparing the AtkObject name
before changing it. 9133117f410c06ad7fa25323a168bc97200043b9 changed
from Equals() to strncmp() to prevent issues related to embedded NUL
bytes, but the change lead to only checking if the AtkObject name has
the new value as prefix. Instead, use strcmp() to check the whole
C strings, but still stopping at the first NUL byte in the new name.
strcmp() has to be safe here, as NS_ConvertUTF16toUTF8::get() has to
return a NUL-terminated string or the code would crash a few lines
below when calling strdup() on it.
