Log Message:
Updated potrace to 1.14.

February 19, 2017: Release 1.14

 This release consists of bugfixes and minor portability improvements.
 A number of bugs triggered by malformed BMP files have been fixed,
 including CVE-2016-8685 and CVE-2016-8686. Error reporting has been
 improved. The image size is now truncated when the bitmap data ends
 prematurely. It is now possible to use negative dy in bitmap
 data. Portability has been improved to encompass C++11. The default
 compiler is now clang if available. Thanks to Nelson Beebe and Martin
 Gieseking for reporting portability issues, and to Agostino Sarubbo
 for reporting bugs.