gdbserver: Use std::list for all_dlls

gdbserver: Use std::list for all_dlls

As a small step towards removing inferior_list/inferior_list_entry, this
patch replaces the usage of inferior_list for the list of dlls by an
std::list.  The dll_info type now uses an std::string for name and has a
simple constructor.

I am able to build gdbserver with mingw on Linux, but I am not able to
test this on a Windows machine (the only platform that uses this code).

gdb/gdbserver/ChangeLog:

	* dll.h: Include <list>.
	(struct dll_info): Add constructor.
	<entry>: Remove field.
	(all_dlls): Change type to std::list<dll_info>.
	* dll.c: Include <algorithm>.
	(get_dll): Remove macro.
	(all_dlls): Change type to std::list<dll_info *>.
	(free_one_dll): Remove.
	(match_dll): Likewise.
	(loaded_dll): Adjust.
	(unloaded_dll): Adjust to all_dlls type change, use
	std::find_if.  Inline code from match_dll.
	(clear_dlls): Adjust to all_dlls type change.
	* server.c (emit_dll_description): Remove.
	(handle_qxfer_libraries): Adjust to all_dlls type change,
	integrate emit_dll_description's functionality.