Add per-thread cache to malloc

* config.make.in: Enable experimental malloc option.
* configure.ac: Likewise.
* configure: Regenerate.
* manual/install.texi: Document it.
* INSTALL: Regenerate.
* malloc/Makefile: Likewise.
* malloc/malloc.c: Add per-thread cache (tcache).
(tcache_put): New.
(tcache_get): New.
(tcache_thread_freeres): New.
(tcache_init): New.
(__libc_malloc): Use cached chunks if available.
(__libc_free): Initialize tcache if needed.
(__libc_realloc): Likewise.
(__libc_calloc): Likewise.
(_int_malloc): Prefill tcache when appropriate.
(_int_free): Likewise.
(do_set_tcache_max): New.
(do_set_tcache_count): New.
(do_set_tcache_unsorted_limit): New.
* manual/probes.texi: Document new probes.
* malloc/arena.c: Add new tcache tunables.
* elf/dl-tunables.list: Likewise.
* manual/tunables.texi: Document them.
* NEWS: Mention the per-thread cache.

configure

@@ -674,6 +674,7 @@ build_obsolete_nsl
 link_obsolete_rpc
 libc_cv_static_nss_crypt
 libc_cv_nss_crypt
+experimental_malloc
 enable_werror
 all_warnings
 force_install
@@ -779,6 +780,7 @@ enable_kernel
 enable_all_warnings
 enable_werror
 enable_multi_arch
+enable_experimental_malloc
 enable_nss_crypt
 enable_obsolete_rpc
 enable_obsolete_nsl
@@ -1450,6 +1452,8 @@ Optional Features:
   --disable-werror        do not build with -Werror
   --enable-multi-arch     enable single DSO with optimizations for multiple
                           architectures
+  --disable-experimental-malloc
+                          disable experimental malloc features
   --enable-nss-crypt      enable libcrypt to use nss
   --enable-obsolete-rpc   build and install the obsolete RPC code for
                           link-time usage
@@ -3522,6 +3526,15 @@ else
 fi
 
 
+# Check whether --enable-experimental-malloc was given.
+if test "${enable_experimental_malloc+set}" = set; then :
+  enableval=$enable_experimental_malloc; experimental_malloc=$enableval
+else
+  experimental_malloc=yes
+fi
+
+
+
 # Check whether --enable-nss-crypt was given.
 if test "${enable_nss_crypt+set}" = set; then :
   enableval=$enable_nss_crypt; nss_crypt=$enableval