cmStandardIncludes: Remove comment about Borland.

The code the comment refers to was removed in commit 2db55ffa (Remove
borland workarounds., 2014-08-06)

Source/cmStandardIncludes.h

@@ -89,17 +89,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-// Borland C++ defines several of the stdlib.h and string.h symbols in
-// sub-headers search.h and mem.h.  These sub-headers have using
-// declarations to pull functions from the std namespace to the global
-// namespace, but they are defined only if the header was not included
-// through the C++-style cstdlib or cstring header.  These outer
-// headers are included by the streams library in C++-style and
-// include blockers are put in place that prevent including the
-// C-style versions from ever including the sub-headers.  Therefore we
-// have to include the sub-headers here to get the using declarations.
-
-
 #if !defined(_WIN32) && defined(__COMO__)
 // Hack for como strict mode to avoid defining _SVID_SOURCE or _BSD_SOURCE.
 extern "C"