Add configure support for linking tcmalloc_minimal and/or jemalloc

Both tcmalloc_minimal and jemalloc outperform the native malloc
implemention on Windows (MSVCRT) in terms of committed memory
consumption (~-30%) and performance (e.g. far less page faults, ~-60%),
depending, of course, on the actual workload.
The longer the download queue, the bigger the impact ;)

On *nix the picture is a little different... tcmalloc usually still
outperforms the native malloc implementation, but not that significantly
than on Windows. jemalloc however is only marginally better than recent
native Linux implementations, while it is already used by some BSD as the
native allocator.

tcmalloc is part of gperftools and very mature and tested by now. It
doesn't work on OSX in the default configuration, however.
http://code.google.com/p/gperftools/

jemalloc is the default allocator at least on FreeBSD and NetBSD and
used in Firefox.
http://www.canonware.com/jemalloc/index.html

configure.ac

@@ -35,6 +35,8 @@ ARIA2_ARG_WITHOUT([libxml2])
 ARIA2_ARG_WITHOUT([libexpat])
 ARIA2_ARG_WITHOUT([libcares])
 ARIA2_ARG_WITHOUT([libz])
+ARIA2_ARG_WITH([tcmalloc])
+ARIA2_ARG_WITH([jemalloc])
 
 ARIA2_ARG_DISABLE([bittorrent])
 ARIA2_ARG_DISABLE([metalink])
@@ -524,6 +526,57 @@ AC_CHECK_FUNCS([__argz_count \
 		utime \
 		utimes])
 
+dnl Put tcmalloc/jemalloc checks after the posix_memalign check.
+dnl These libraries may implement posix_memalign, while the usual CRT may not
+dnl (e.g. mingw). Since we aren't including the corresponding library headers
+dnl this will lead to undefined posix_memalign() errors when compiling
+if test "x$with_tcmalloc_requested" = "xyes" &&
+   test "x$with_jemalloc_requested" = "xyes"; then
+  AC_MSG_FAILURE([Cannot use both, tcmalloc and jemalloc!])
+fi
+
+if test "x$with_tcmalloc" = "xyes"; then
+  dnl Important: put malloc libs at the very end.
+  dnl Only newish versions have a .pc, thus try CHECK_LIB as well.
+  PKG_CHECK_MODULES([TCMALLOC], [libtcmalloc_minimal], [have_tcmalloc=yes], [have_tcmalloc=no])
+  if test "x$have_tcmalloc" = "xyes"; then
+    CPPFLAGS="$TCMALLOC_CFLAGS $CPPFLAGS"
+    LDFLAGS="$TCMALLOC_LDFLAGS $CPPFLAGS"
+    LIBS="$LIBS $TCMALLOC_LIBS"
+  else
+    AC_CHECK_LIB([tcmalloc_minimal], [malloc], [have_tcmalloc=yes], [have_tcmalloc=no])
+    if test "x$have_tcmalloc" = "xyes"; then
+      LIBS="$LIBS -ltcmalloc_minimal"
+    else
+      if test "x$with_tcmalloc_requested" = "xyes"; then
+        ARIA2_DEP_NOT_MET([tcmalloc_minimal])
+      fi
+    fi
+  fi
+fi
+
+if test "x$have_tcmalloc" != "xyes" && test "x$with_jemalloc" = "xyes"; then
+  dnl Important: put malloc libs at the very end.
+  dnl Usually jemalloc does not come with a .pc, as the official source does not
+  dnl generate one.
+  PKG_CHECK_MODULES([JEMALLOC], [jemalloc], [have_jemalloc=yes], [have_jemalloc=no])
+  if test "x$have_jemalloc" = "xyes"; then
+    CPPFLAGS="$JEMALLOC_CFLAGS $CPPFLAGS"
+    LDFLAGS="$JEMALLOC_LDFLAGS $CPPFLAGS"
+    LIBS="$LIBS $JEMALLOC_LIBS"
+  else
+    AC_CHECK_LIB([jemalloc], [malloc], [have_jemalloc=yes], [have_jemalloc=no])
+    if test "x$have_jemalloc" = "xyes"; then
+      LIBS="$LIBS -ljemalloc"
+    else
+      if test "x$with_jemalloc_requested" = "xyes"; then
+        ARIA2_DEP_NOT_MET([jemalloc (unprefixed)])
+      fi
+    fi
+  fi
+fi
+
+
 if test "x$enable_epoll" = "xyes"; then
   AC_CHECK_FUNCS([epoll_create], [have_epoll=yes])
   if test "x$have_epoll" = "xyes"; then