Another "Do not export whole class to avoid MS C++ implicitly exporting...

...base template" (like a90d4d5f did for
OSLOutputStreamWrapper), in preparation for
<https://gerrit.libreoffice.org/#/c/31679> "tdf#88206 replace
cppu::WeakImplHelper* in unotools".

Beats me why a solution like 4f918cd5
"comphelper: give up on the XPropertySetInfos for now" apparently doesn't work
there---almost feels like MSVC recursively treats as dllexport'ed all the (non-
llim-/export'ed) base classes all the way down until reaching a template.

Change-Id: Id42610e7fd5c5762dffdeb15623bfe3a37ec0aa6
Reviewed-on: https://gerrit.libreoffice.org/31732Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

include/comphelper/oslfile2streamwrap.hxx

@@ -32,13 +32,12 @@ namespace comphelper
 // FmUnoIOStream,
 // Stream to read and write data, based on File
 
-class COMPHELPER_DLLPUBLIC OSLInputStreamWrapper : public ::cppu::WeakImplHelper<css::io::XInputStream>
+class OSLInputStreamWrapper : public ::cppu::WeakImplHelper<css::io::XInputStream>
 {
-    ::osl::Mutex    m_aMutex;
-    ::osl::File*    m_pFile;
-
 public:
-    OSLInputStreamWrapper(::osl::File& _rStream);
+    COMPHELPER_DLLPUBLIC OSLInputStreamWrapper(::osl::File& _rStream);
+
+private:
     virtual ~OSLInputStreamWrapper() override;
 
 // css::io::XInputStream
@@ -47,6 +46,9 @@ public:
     virtual void        SAL_CALL    skipBytes(sal_Int32 nBytesToSkip) throw(css::io::NotConnectedException, css::io::BufferSizeExceededException, css::uno::RuntimeException, std::exception) override;
     virtual sal_Int32   SAL_CALL    available() throw(css::io::NotConnectedException, css::uno::RuntimeException, std::exception) override;
     virtual void        SAL_CALL    closeInput() throw(css::io::NotConnectedException, css::uno::RuntimeException, std::exception) override;
+
+    ::osl::Mutex    m_aMutex;
+    ::osl::File*    m_pFile;
 };