Symlinks instead of copies in autogen.sh
Cleanup .gitignore
Add success message to autogen.sh
Fix m4 warnings from autotools
Major update of build system

- depends of automake 1.11
- C99
- pic-only
- more warning C flags
- remove obscure checks
- don't print directories
- add libmodbus.pc to clean files
- remove -Werror
Fix all compilations warnings spotted by new compilation flags
Switch README from ReST to Markdown
Minor change to README
Clean generated documentation on distclean
Update references to README.md
Revert to gzip file for distribution (tar -Jvf *.xz is not convenient)
Fix stupid sizeof on char*

Thanks Giampaolo Bellini.
Use nonblocking sockets on Win32 and OS X/iOS too
Remove blank line from previous commit