add a HACKING file with some initial notes on code style and correctness
add a HACKING file with some initial notes on code style and correctness

fanc999/libsoup,jwendell/libsoup,jwendell/libsoup,jwendell/libsoup,Distrotech/libsoup,Distrotech/libsoup,fanc999/libsoup,Distrotech/libsoup,fanc999/libsoup,Distrotech/libsoup,jwendell/libsoup,fanc999/libsoup,ahmedammar/platform_external_gst_libsoup,jwendell/libsoup,ahmedammar/platform_external_gst_libsoup,fanc999/libsoup,Distrotech/libsoup,ahmedammar/platform_external_gst_libsoup