Fix CGIFormData to actually store file-upload part content

File-upload parts (Content-Disposition with filename=) were
unconditionally flagged currentSkip and discarded at PART_BOUNDARY,
so every <field type="file"> upload site (track audio, presets,
project icons) only ever received an empty value via $[fieldname],
never the real uploaded bytes.

CGIFormData.cpp

@@ -24,8 +24,6 @@ namespace coreutils {
       MString disposition = fields[MString("Content-Disposition")];
       ZString dz(disposition.getData(), disposition.getLength());
 
-      currentSkip = (dz.find(ZString("filename=\"")) != -1);
-
       int namePos = dz.find(ZString("name=\""));
       if (namePos != -1) {
          ZString afterName = dz.substring(namePos + 6);
@@ -117,10 +115,17 @@ namespace coreutils {
           if (pos < 0)
              return Status::INCOMPLETE;
           char *bodyEnd = buffer.getCursor();
-          if (!currentSkip && currentName.getLength() > 0)
+          // A part whose Content-Disposition includes filename="..."
+          // (a real <input type="file">) used to be silently discarded
+          // here (currentSkip) rather than stored like any other part -
+          // every existing <field type="file"> upload (track audio,
+          // presets, project icons) has therefore never actually
+          // received real file content via $[fieldname], only ever an
+          // empty value. Storing it the same way as any other part is
+          // exactly what those call sites already assume.
+          if (currentName.getLength() > 0)
              storeValue(currentName, MString(ZString(bodyStart, bodyEnd - bodyStart)));
           currentName = MString();
-          currentSkip = false;
           state = PART_BOUNDARY;
           return Status::DATA_AVAIL;
        }