sha.cpp compiler warnings

[Chad Yates]

When compiling sha.cpp under under MS Visual Studio 6.0 I recieve the
following Level 2 warnings:

sha.cpp
..\include\cc++/digest.h(406) : warning C4275: non dll-interface class
'ost::SHA64DigestHelper' used as base for dll-interface class
'ost::SHA1Digest'
        ..\include\cc++/digest.h(381) : see declaration of
'SHA64DigestHelper'

..\include\cc++/digest.h(424) : warning C4275: non dll-interface class
'ost::SHA64DigestHelper' used as base for dll-interface class
'ost::SHA256Digest'
        ..\include\cc++/digest.h(381) : see declaration of
'SHA64DigestHelper'

..\include\cc++/digest.h(424) : warning C4275: non dll-interface class
'ost::SHAConstant' used as base for dll-interface class 'ost::SHA256Digest'
        ..\include\cc++/digest.h(320) : see declaration of 'SHAConstant'

I don't know if this will negatively affect the dll or if it is just a
meaningless microsoft warning.

Since I'm not an expert on dlls and object-oriented programming, could
someone make a call on this.  I'd be interested to know if it is an issue or
not.

,chad