Ensure the Encode/Decode APIs can deal with any buffer that can fit
in memory.

Change-Id: I3ecc50d5b9419a36f95b0888c71e0309a8cb674a

This converts the KWSys license to a pure 3-clause OSI-approved BSD
License.  We drop the previous license clause requiring modified
versions to be plainly marked.  We also update the KWSys copyright to
cover the full development time range.

All KWSys C symbol names begin with the KWSYS_NAMESPACE defined at
configuration time.  For ease of editing we write canonical names with
the prefix 'kwsys' and use macros to map them to the configured prefix
at preprocessing time.  In the case of standalone KWSys, the prefix is
'kwsys', so the macros were previously defined to their own names.

We now skip defining the macros in the identity case so that the final
symbol names are never themselves macros.  This will allow the symbols
to be further transformed behind the scenes to help linkers in special
cases on some platforms.

ENH: Moved kwsys_ns and kwsysEXPORT macros to Configure.h in the case of building a kwsys source file.  This allows more than one header to be included in a kwsys source file without redefining the macros.

ERR: Avoiding namespace pollution: kw_sys -> kwsys_ns.  Also undefining the macro at the correct time.

ERR: On Borland preprocessor goes into recursion which adds some weid spaces in the include name. This fixes it

ERR: Reduced requirements on preprocessor for export macro due to limitations of Mac preprocessor.  The preprocessor can be fixed by using -no-cpp-precomp, but we don't want to require that option for every source file that includes our headers.