res_pjsip: Add fax_detect_timeout endpoint option.

The new endpoint option allows the PJSIP channel driver's fax_detect
endpoint option to timeout on a call after the specified number of
seconds into a call.  The new feature is disabled if the timeout is set
to zero.  The option is disabled by default.

ASTERISK-26214
Reported by: Richard Mudgett

Change-Id: Id5a87375fb2c4f9dc1d4b44c78ec8735ba65453d

contrib/ast-db-manage/config/versions/4a6c67fa9b7a_add_fax_detect_timeout_option.py

@@ -0,0 +1,23 @@
+"""add fax_detect_timeout option
+
+Revision ID: 4a6c67fa9b7a
+Revises: 9deac0ae4717
+Create Date: 2016-07-18 18:20:44.249491
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '4a6c67fa9b7a'
+down_revision = '9deac0ae4717'
+
+from alembic import op
+import sqlalchemy as sa
+
+
+def upgrade():
+    op.add_column('ps_endpoints', sa.Column('fax_detect_timeout', sa.Integer))
+
+
+def downgrade():
+    op.drop_column('ps_endpoints', 'fax_detect_timeout')
+