#82 Wrong calculation of frames in bacapp_data_len

[Maria]

When sending 2 sets of opening & closing tags (one with context number 3 and the other with 0), current function bacapp_data_len returns number of frames 1, and should return 2.
There was created a pull request regarding this issue.
https://github.com/bacnet-stack/bacnet-stack/pull/491
How to reproduce:
Invoke WriteProperty with values:

• Opening tag, context tag = 3
• Opening tag, context tag = 0
• Closing tag, context tag = 0
• Closing tag, context tag = 3