Avoid false positives w/ overlapping memcpy args with _FORTIFY_SOURCE's
memcpy_chk.

https://src.fedoraproject.org/rpms/valgrind/raw/rawhide/f/valgrind-3.21.0-no-memcpy-replace-check.patch
https://bugs.kde.org/show_bug.cgi?id=402833
https://bugs.kde.org/show_bug.cgi?id=453084
--- a/shared/vg_replace_strmem.c
+++ b/shared/vg_replace_strmem.c
@@ -1128,7 +1128,7 @@ static inline void my_exit ( int x )
    MEMMOVE_OR_MEMCPY(20181, soname, fnname, 0)
 
 #define MEMCPY(soname, fnname) \
-   MEMMOVE_OR_MEMCPY(20180, soname, fnname, 1)
+   MEMMOVE_OR_MEMCPY(20180, soname, fnname, 0) /* See KDE bug #402833 */
 
 #if defined(VGO_linux)
  /* For older memcpy we have to use memmove-like semantics and skip
@@ -1714,8 +1714,6 @@ static inline void my_exit ( int x )
       RECORD_COPY(len); \
       if (len == 0) \
          return dst; \
-      if (is_overlap(dst, src, len, len)) \
-         RECORD_OVERLAP_ERROR("memcpy_chk", dst, src, len); \
       if ( dst > src ) { \
          d = (HChar *)dst + len - 1; \
          s = (const HChar *)src + len - 1; \