Fixed a crash when returning a string from librtlsdr to mono.
Fixed a crash when returning a string from librtlsdr to mono.

git-svn-id: 6b7e1e5d0861e268462ba7828ef63c1bcab52a9b@325 d3cde5d6-82b8-4669-8b62-43054d6781d8

cgommel/sdrsharp,periloso/sdrsharp