conv_gen: Use python2 to execute the script

The script does not work with python3:

$ python3 utils/conv_gen.py
  File "utils/conv_gen.py", line 124
    def _print_term(self, fi, num_states, pack = False):

Second there is no 'python' on FreeBSD and one needs to select
the major version to use.

  GEN      conv_cs3_gen.c
  GEN      conv_xcch_gen.c
  GEN      conv_cs2_gen.c
python: not found
python: not found
python: not found

By using python2 we solve both issues. On Debian python2 is located
inside the python-minimal package.

1 files changed, 1 insertions, 1 deletions

diff --git a/utils/conv_gen.py b/utils/conv_gen.py
index 1377fcae..bb547de8 100644
--- a/utils/conv_gen.py
+++ b/utils/conv_gen.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2
 
 mod_license = """
 /*