Fix first paragraph of the 'About environment variables' appendix

[ci:skip]
Fix 'rake native_support:clean'. Closes GH-1264
Add more trace points
Remove trailing whitespaces from some files
Do not crash when detaching a process that is already being detached.
Remove trailing whitespace from some more files

[ci:skip]
Remove trailing whitespace from some more files

[ci:skip]
Upgrade preferred Nginx version to 1.6.1.
Remove trailing whitespaces from some files
Escape code revision XML data
Remove trailing whitespace from some files
Allow the loaders to work even without a generation_dir option.
Introduce ServerKit, MemoryKit and some new data structures
Continue working on ServerKit.
Continue working on ServerKit.
Various ServerKit optimizations

- Reduce number of reference count manipulations in FileBufferedChannel
- Use raw system calls instead of OXT wrappers. This reduces the number
  of atomic operations
- Reorder some code for better cache locality
Update Channel documentation and add unit tests for it
Add unit tests for LString
Add unit tests for mbuf
Add unit tests for HeaderTable