Strangely, we *do* need to define ZLIB_DLL.
Do it in the project file rather than in the source,
so it's easier for Mark to change.
diff --git a/PCbuild/zlib.dsp b/PCbuild/zlib.dsp
index cfb1cf0..559be91 100644
--- a/PCbuild/zlib.dsp
+++ b/PCbuild/zlib.dsp
@@ -44,7 +44,7 @@
# PROP Target_Dir ""
F90=df.exe
# ADD BASE CPP /nologo /MT /W3 /GX /O2 /D "WIN32" /D "NDEBUG" /D "_WINDOWS" /YX /FD /c
-# ADD CPP /nologo /MD /W3 /GX /Zi /O2 /I "..\Include" /I "..\PC" /I "..\..\zlib113" /D "NDEBUG" /D "WIN32" /D "_WINDOWS" /YX /FD /c
+# ADD CPP /nologo /MD /W3 /GX /Zi /O2 /I "..\Include" /I "..\PC" /I "..\..\zlib113" /D "NDEBUG" /D "WIN32" /D "_WINDOWS" /D "ZLIB_DLL" /YX /FD /c
# ADD BASE MTL /nologo /D "NDEBUG" /mktyplib203 /o "NUL" /win32
# ADD MTL /nologo /D "NDEBUG" /mktyplib203 /o "NUL" /win32
# ADD BASE RSC /l 0x409 /d "NDEBUG"
@@ -72,7 +72,7 @@
# PROP Target_Dir ""
F90=df.exe
# ADD BASE CPP /nologo /MTd /W3 /Gm /GX /Zi /Od /D "WIN32" /D "_DEBUG" /D "_WINDOWS" /YX /FD /c
-# ADD CPP /nologo /MDd /W3 /Gm /GX /Zi /Od /I "..\Include" /I "..\PC" /I "..\..\zlib113" /D "_DEBUG" /D "WIN32" /D "_WINDOWS" /YX /FD /c
+# ADD CPP /nologo /MDd /W3 /Gm /GX /Zi /Od /I "..\Include" /I "..\PC" /I "..\..\zlib113" /D "_DEBUG" /D "WIN32" /D "_WINDOWS" /D "ZLIB_DLL" /YX /FD /c
# ADD BASE MTL /nologo /D "_DEBUG" /mktyplib203 /o "NUL" /win32
# ADD MTL /nologo /D "_DEBUG" /mktyplib203 /o "NUL" /win32
# ADD BASE RSC /l 0x409 /d "_DEBUG"