Replace MEMPCPY_P with USE_AS_MEMPCPY in i586 memcpy.S to support i386
multi-arch memcpy. Also we should check SHARED not PIC for libc.so
since libc.a may be compiled with PIC.
* sysdeps/i386/i586/memcpy.S (MEMPCPY_P): Removed.
Check USE_AS_MEMPCPY/SHARED instead of MEMPCPY_P/PIC.
* sysdeps/i386/i586/mempcpy.S (USE_AS_MEMPCPY): New.