lstm: Initialize member variable input_width_

Coverity report:

CID 1366452 (#1 of 1): Uninitialized scalar field (UNINIT_CTOR)
18. uninit_member: Non-static class member input_width_ is not initialized
 in this constructor nor in any functions that it calls.

Signed-off-by: Stefan Weil <sw@weilnetz.de>

lstm/lstm.cpp

@@ -74,7 +74,8 @@ LSTM::LSTM(const STRING& name, int ni, int ns, int no, bool two_dimensional,
       ns_(ns),
       nf_(0),
       is_2d_(two_dimensional),
-      softmax_(NULL) {
+      softmax_(NULL),
+      input_width_(0) {
   if (two_dimensional) na_ += ns_;
   if (type_ == NT_LSTM || type_ == NT_LSTM_SUMMARY) {
     nf_ = 0;