skyblue water color, in Math.h, common for game and editor

[cryham]

Changed water color to darker and skyblue, moved to Math.h and did same for editor.

[mgerhardy]

getting a lot of compiler warnings here.

/home/mgerhardy/dev/oss/caveexpress/src/modules/common/IFrontend.h: In member function ‘virtual bool IFrontend::renderWaterPlane(int, int, int, int, const float (&)[4], const float (&)[4])’:
/home/mgerhardy/dev/oss/caveexpress/src/modules/common/IFrontend.h:107:105: warning: declaration of ‘waterLineColor’ shadows a global declaration [-Wshadow]
  107 |         virtual bool renderWaterPlane (int x, int y, int w, int h, const Color& fillColor, const Color& waterLineColor) {
      |                                                                                            ~~~~~~~~~~~~~^~~~~~~~~~~~~~
In file included from /home/mgerhardy/dev/oss/caveexpress/src/modules/common/IFrontend.h:6:
/home/mgerhardy/dev/oss/caveexpress/src/modules/common/Math.h:105:20: note: shadowed declaration is here
  105 | static const Color waterLineColor =

[mgerhardy]

new:

versus old:

maybe we should make the color of the water depend on the theme of the map

[cryham]

maybe we should make the color of the water depend on the theme of the map

Good idea. I think for later.
I'll fix the warning.

[cryham]

This should fix the warning