Proposed commit log message:
```
devel/ipython: Update to 6.5.0
- devel/ipython is now tracking 6.x mainline
- Previous version of ipython (5.x series) moved to devel/ipython5
- It is based on pure Python 3.3+ codebase
- Supports latest Python 3.7
- Remove GCC dependency since it now build with CLANG
More information about new features as well as backward incompatible changes [1]
[1] https://ipython.readthedocs.io/en/stable/whatsnew/version6.html
#Reviewed by: koobs, mat
Approved by: ?
#Differential Revision: https://reviews.freebsd.org/D16508/
```