Add 64-bit Silvermont-optimized string/memory functions.

Add following functions:
bcopy, bzero, memcpy, memmove, memset, stpcpy, stpncpy, strcat, strcpy,
strlen, strncat, strncpy, memcmp, strcmp, strncmp.
Set all these functions as the default ones.

Change-Id: Ic66b250ad8c349a43d25e2d4dea075604f6df6ac
Signed-off-by: Varvara Rainchik <varvara.rainchik@intel.com>

libc/arch-x86_64/string/cache.h

@@ -0,0 +1,36 @@
+/*
+Copyright (c) 2014, Intel Corporation
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright notice,
+    * this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above copyright notice,
+    * this list of conditions and the following disclaimer in the documentation
+    * and/or other materials provided with the distribution.
+
+    * Neither the name of Intel Corporation nor the names of its contributors
+    * may be used to endorse or promote products derived from this software
+    * without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+/* Values are optimized for Silvermont */
+#define SHARED_CACHE_SIZE	(1024*1024)			/* Silvermont L2 Cache */
+#define DATA_CACHE_SIZE		(24*1024)			/* Silvermont L1 Data Cache */
+
+#define SHARED_CACHE_SIZE_HALF	(SHARED_CACHE_SIZE / 2)
+#define DATA_CACHE_SIZE_HALF	(DATA_CACHE_SIZE / 2)