py-bcrypt: add legacysupport for getentropy

[nilFinx]

Closes: https://trac.macports.org/ticket/70370

Description

This adds the legacysupport portgroup version 1.1 with newest_darwin_requires_legacy set to 15 (OSX 10.11) to fix a build issue for missing getentropy.

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 10.9.5 13F1911 x86_64
Xcode 6.2 6C131e

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@stromnov for port py-bcrypt.