aria2 - HTTP/FTP/Metalink/BitTorrent ダウンロード ユーティリティ

* Use AM subdir-objects

Doing so in AM_INIT_AUTOMAKE seems to be the most compatible way of
doing so.

Closes GH-120

* AM_SILENT_RULES([yes]) with backwards-compatiblity

Supported since automake-1.11. There is no point in having the very
verbose compile stuff running about, which cannot even silenced
properly with `make -s` by default. Otherwise, `make V=1` or
`--disable-silent-rules` are your friends

* Fix automake-1.14 am_aux_dir

AC_USE_SYSTEM_EXTENSIONS will cause AC_PROG_CC, which is overridden
by automake-1.14, which will then init (part) of automake, in
particular am_aux_dir expansion, which in turn relies on ac_aux-dir,
which is not initialized at this point, and thus: certain doom (or
fun, depending on your POV and mood :p)

Hence call AC_USE_SYSTEM_EXTENSIONS only after
AM_INIT_AUTOMAKE. This, of course, caused a lot of related macro
shuffling.

Tested against automake-1.10 (OSX Lion/XCode version) and
automake-1.14 (homebrew version)

* Require external gettext for --enable-nls

And stop using the internal flavor with ./intl

* Make AX_CXX_COMPILE_STDCXX_11 test for -stdlib=libc++ via std::shared_ptr

The clang shipped with OSX XCode and clangs not build enabling
libcpp, will default to the libstdc++ headers and lib installed on
the system. In the OSX case, that libstdc++ is the one bundles with
gcc-4.2, which is far too old to provide all required C++11 types,
such as std::shared_ptr. Hence, the C++11 check should try to
compile a program with a C++11 type and try -stdlib=libc++ if the
default lib fails to compile said program.

* Make the configure check for C++11 compiler mandatory

Remove stray "dnl", so that mandatory actually works with (my)
autoreconf.

* Always build doc/manual-src

Should sphinx-build be not available AND the man file not be prsent,
then just "touch" it into existence (and warn about that)

* Win: Use SetConsoleCtrlHandler for SIGINT/SIGTERM

* Implement a simple resource lock (threading)

In this initial implementation Locks are no-ops on platforms other
than Windows.

* Check for sphinx-build during configure

* Add --with-disk-cache configure option

Enables packagers more fine grained control over the default value
without having to mess with config files.

See GH-115

* Change defaults: Enable 16M disk cache by default.

* Always save control file if --force-save is given

* Set log level DEBUG for unittests

* Check that C++ compiler supports override keyword

If the compiler supports override, define CXX11_OVERRIDE as
override, otherwise define it as empty. Use CXX11_OVERRIDE instead
of override.

* AppleTLS: Fix MessageDigestImpl

* AppleTLS: Fix session CFRelease stuff

* Use AX_CXX_COMPILE_STDCXX_11 macro to detect C++0x/C++11 support in
compiler

* Require -std=c++11 and use std::shared_ptr instead of SharedHandle

* Join URI on redirect

* Send HAVE message to the peer which the piece is downloaded from

Historically, aria2 did not send HAVE message to the peer which the
piece is coming from, thinking it is obvious that the peer knows we
have the piece. But it is not obvious if one piece is download from
more than 1 peers (e.g., end game mode). So it is better to send
HAVE to all peers connected.

* Improvements to --follow-torrent=false documentation.

Patch from gt

* SessionSerializer: Truly unique URIs

Before, only spent uris where sanitized not to be contained within
remaining uris. Change this so that each uri in the
union(remaining,spent) get saved once at most. The order of the
uris will won't be changed, with remaining uris going first followed
by spent uris.

Also avoid copying the uri std::strings around during dupe checking,
usually resulting in better performance regarding CPU and space.

* Make getOption RPC method return option for stopped downloads

* SessionSerializer: Save spent URIs as well as remaining ones