audio/bjumblr-lv2: fix build on GCC architectures

Require C++11 compiler because of -std=c++11.

Include climits in FileChooser.hpp because of INT64_MAX (GCC doesn't do that by default).

PR: 248134
Approved by: portmgr (blanket: build fix)
MFH: 2020Q3 (blanket: build fix)