I changed SvCacheStream class to SvMemoryStream class in
the following:  MSE40HTMLClipFormatObj, SfxLockBytesItem,
SwEditShell, INetMIMEMessageStream classes,
MakeLockBytes_Impl function and SwUnoCursorHelper namespace.
I modified header the precompiled_sw.hxx, wrtsh1.cxx, unoobj2.cxx.
I added two functions in SvMemoryStream class: GetBuffer and
GetSize, and I renamed the old GetSize function to GetBufSize.
I deleted SvCacheStream class.

Change-Id: I929236538dfbe23cccfd1eb85f10c1d5411baa8d
Reviewed-on: https://gerrit.libreoffice.org/4847Reviewed-by: Andras Timar <atimar@suse.com>
Tested-by: Andras Timar <atimar@suse.com>