Remove "int options, const char *const *options, unsigned option_flags"
arguments from every New() functions since these args are mainly unused. You
now have to call input_item_AddOptions after input item creation to add
options.

Add input_item_net_type enum in order to avoid confusion between 2 int
arguments: i_duration and i_net that could both be -1, 0 or > 0.

Replace input_item_NewWithType and input_item_NewWithTypeExt with
input_item_NewExt.

Add input_item_NewCard, input_item_NewDisc, input_item_NewStream,
input_item_NewDirectory, input_item_NewFile MACRO. These MACROS avoid to use
useless arguments for an item type (for example, it's useless to specify a
duration for a directory type).