GNU Guile-CV 0.3.1 release

Hello, GNU Guile-CV 0.3.1 is released. This is a maintenance release, which fixes a bug in the =pre-inst-env= script, which is used by Guile-CV at build time and may also be used to test and run an uninstalled Guile-CV instance. [ for those who wouldn't know [ the message is marked-up using

Re: [PATCH] Support C99 complex types in (system foreign)

Applied with some style changes in 496f69dba2fdf1720b40349932fcdecd444107c3.