Fix compiler warnings for -Wimplicit-int-float-conversion

longやunsigned longの変数をdoubleに暗黙的に変換している箇所は精度が失う可能性があるとclangに指摘されたため明示的にキャストstatic_cast<double>()を使いコンパイラに意図した変更であると伝えます。

clang 17のレポート (file pathを一部省略)

src/article/drawareabase.cpp:5452:46: warning: implicit conversion from 'gint64' (aka 'long') to 'double' may lose precision [-Wimplicit-int-float-conversion]
 5452 |     m_deceleration.elapsed += ( current_time - m_deceleration.last_time ) * kDecelerationRatio;
      |                                 ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~   ~
src/image/imageadmin.cpp:850:44: warning: implicit conversion from 'size_type' (aka 'unsigned long') to 'double' may lose precision [-Wimplicit-int-float-conversion]
  850 |         double upper =  m_list_view.size() * ICON_SIZE;
      |                ~~~~~    ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~

JDimproved / JDim

Fix compiler warnings for -Wimplicit-int-float-conversion #1373