This file was broken in ada65567.

Change-Id: Ib75664194491643f8e4f1503a2ed942a2d1e1655

perf: String#getBytes(Charset) vs getBytes(String)

Better support for cross-compilation

Build scripts to publish precompiled protoc binaries (Maven-based)

Run make protoc(.exe) instead of just make, because the latter fails on Cygwin with mingw gcc; build-protoc.sh works under Cygwin; build-protoc.sh will use the --host parameter consistent with what os-maven-plugin has detected

Fix raise and except syntax issues for py3

Clean up generated files

This fixes the problem where `make check` generates files not ignored
by `.gitignore`.

Delete "SEBS" (aka: Clean up Kenton's old trash)

The file `SEBS` is a build file for a toy build system I was writing in my spare time six years ago, back when I maintained protobufs. Arguably it was never appropriate for me to have placed this file in the protobuf tree, but it was convenient at the time and didn't seem to hurt anything. It clearly doesn't belong here now, though.

Change-Id: I4a8dcb4aba0104305b5dd052ed3bd532ddbedfb2