Don't copy filepath to buf. [coverity]

No modification was being done to buf after the copy of filepath.
It was just being passed to fopen. As such the copy is redundant,
and can lead to buffer overflow issues if the specified filepath
is larger than buf.

src/libespeak-ng/compilembrola.c

 	int mbrola_ctrl = 20; // volume in 1/16 ths
 	MBROLA_TAB data[N_PHONEME_TAB];
 
-	strcpy(buf, filepath);
-	if ((f_in = fopen(buf, "r")) == NULL)
-		return create_file_error_context(context, errno, buf);
+	if ((f_in = fopen(filepath, "r")) == NULL)
+		return create_file_error_context(context, errno, filepath);
 
 	while (fgets(buf, sizeof(phoneme), f_in) != NULL) {
 		buf[sizeof(phoneme)-1] = 0;