Get rid of Windows-specific stuff.

diff --git a/GNUmakefile b/GNUmakefile
index 4de9d10..ff4789a 100755
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -656,7 +656,7 @@ nolib: $(OBJS)
 dll: cryptest.import.exe dlltest.exe
 
 cryptopp.dll: $(DLLOBJS)
-	$(CXX) -shared -o $@ $(CXXFLAGS) $(DLLOBJS) $(LDFLAGS) $(LDLIBS) -Wl,--out-implib=libcryptopp.dll.a
+	$(CXX) -shared -o $@ $(CXXFLAGS) $(DLLOBJS) $(LDFLAGS) $(LDLIBS)
 
 libcryptopp.import.a: $(LIBIMPORTOBJS)
 	$(AR) $(ARFLAGS) $@ $(LIBIMPORTOBJS)
diff --git a/dll.cpp b/dll.cpp
index 72dade9..b5097ab 100644
--- a/dll.cpp
+++ b/dll.cpp
@@ -48,7 +48,7 @@ NAMESPACE_END
 
 #endif
 
-#ifdef CRYPTOPP_EXPORTS
+#if defined CRYPTOPP_EXPORTS && defined _MSC_VER
 
 USING_NAMESPACE(CryptoPP)