Python 3's print requires to use parentheses, so this patch adds them
where they were missing.
gdb/testsuite/ChangeLog:
* gdb.ada/py_range.exp: Add parentheses to calls to print.
* gdb.dwarf2/symtab-producer.exp: Same.
* gdb.gdb/python-interrupts.exp: Same.
* gdb.gdb/python-selftest.exp: Same.
* gdb.python/py-linetable.exp: Same.
* gdb.python/py-type.exp: Same.
* gdb.python/py-value-cc.exp: Same.
* gdb.python/py-value.exp: Same.