Add 32-bit Silvermont-optimized string/memory functions.
Add following functions:
bcopy, memcpy, memmove, memset, bzero, memcmp, wmemcmp, strlen,
strcpy, strncpy, stpcpy, stpncpy.
Create new directories inside arch-x86 to specify architecture: atom,
silvermont and generic (non atom or silvermont architectures are treated like generic).
Due to introducing optimized versions of stpcpy and stpncpy,
c-implementations of these functions are moved from
common for architectures makefile to arm and mips specific makefiles.
Change-Id: I990f8061c3e9bca1f154119303da9e781c5d086e
Signed-off-by: Varvara Rainchik <varvara.rainchik@intel.com>