Peter M. Groen / libmodbus

- 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

Thanks to Damian Zieliński.

Add standalone Makefiles for the modbus DLL and tests, using the modbus DLL.

Thanks to Bill Gray.

Thanks to Denis Davydov

Fix EXXX values defined in Microsoft C Runtime 10

Thanks to Carlos Tangerino

Thanks to oldfaber

Thanks to oldfaber.

Original patch provided by Michael Haberler <git@mah.priv.at>.