Fixed Makefile to support Cygwin(windows), added Prefix and Shared Varia...

...ble and added Libpiano build shortcut.

Should support building on Cygwin with Gnu-GCC, without trouble.

NOTE: Sorry for the earlier request had a bug with Linux and GCC -std=gnu99, support is not fluent across platforms. as well as CC preset didnt work as expected across platforms. had to revert after testing.