DRM Helper API: Changes

The following header file(s) have changed between 3.0 and 3.1

**Table 1:** drmhelper.h
Type	Class	Change
New enum	`TDRMHelperPreviewMediaType`
New public method	`CDRMHelper`	`TInt HandleErrorOrPreviewL(TInt aError, RFile& aFile, HBufC8*& aEmbeddedPreviewUri );`
New public method	`CDRMHelper`	`TInt HandleErrorOrPreviewL(TInt aError, const TDesC& aFileName, HBufC8*& aEmbeddedPreviewUri);`
New public method	`CDRMHelper`	`TInt SetPreviewMediaType(TDRMHelperPreviewMediaType aMediaType );`

The following header file(s) have changed between 3.1 and 3.2

**Table 2:** drmhelper.h
Type	Class	Change
Changed namespace	`using namespace ContentAccess;`