This happens because multiline strings used to be allowed in older GCC versions, but not in newer ones. To fix it, just rewrite the help function as follows:

static void help(void)
{
printf("tdbtool:\n");
printf (" create dbname : create a database\n");
printf (" open dbname : open an existing database\n");
printf (" erase : erase the database\n");
printf (" dump dumpname : dump the database as strings\n");
printf (" insert key data : insert a record\n");
printf (" store key data : store a record (replace)\n");
printf (" show key : show a record by key\n");
printf (" delete key : delete a record by key\n");
printf (" list : print the database hash table and freelist\n");
printf (" free : print the database freelist\n");
printf (" 1 | first : print the first record\n");
printf (" n | next : print the next record\n");
printf (" q | quit : terminate\n");
printf (" \\n : repeat 'next' command\n");
}