title: cimg lib for android compile error
body: <p>I try to compile CImg for android. But Got such errors when compile it.</p>
  
  <p>that is part of the Application.mk
  `</p>
  
  <pre><code>APP_STL := gnustl_static 
  NDK_TOOLCHAIN_VERSION=4.9 
  APP_CPPFLAGS +=-std=c++11
  APP_ABI := armeabi armeabi-v7a 
  APP_CPPFLAGS += -frtti
  APP_CPPFLAGS += -fexceptions
  APP_CPPFLAGS += -DANDROID
  
  APP_OPTIM := release
  LOCAL_ARM_MODE := thumb 
  </code></pre>
  
  <p>I got following errors</p>
  
  <pre><code>/CImg.h: In member function 'cimg_library::CImg&lt;typename cimg_library::cimg::last&lt;T, int&gt;::type&gt;
   cimg_library::CImg&lt;T&gt;::_get_select(cimg_library::CImgDisplay&amp;, const char*, unsigned int, unsigned int*, int, int, int, bool, bool) const':
  ./CImg.h:38224:15: error: expected unqualified-id before numeric constant
             _X = (int)X, _Y = (int)Y, _Z = (int)Z,
             ^
  In file included /test.cpp:2069:
  ./CImg.h:38249:32: error: 'yf' was not declared in this scope
             visu.draw_line(0,yf,visu.width() - 1,yf,foreground_color,0.7f,0xFF00FF00).
  ./CImg.h:38251:27: error: 'xf' was not declared in this scope
               draw_line(xf,0,xf,visu.height() - 1,foreground_color,0.7f,0xFF00FF00).
  ./CImg.h:38254:32: error: 'zxf' was not declared in this scope
               visu.draw_line(zxf,0,zxf,yM,foreground_color,0.7f,0xFF00FF00).
                              ^
  ./CImg.h:38254:42: error: 'yM' was not declared in this scope
               visu.draw_line(zxf,0,zxf,yM,foreground_color,0.7f,0xFF00FF00).
                                        ^
  ./CImg.h:38256:31: error: 'zyf' was not declared in this scope
                 draw_line(0,zyf,xM,zyf,foreground_color,0.7f,0xFF00FF00).
                             ^
  ./CImg.h:38256:35: error: 'xM' was not declared in this scope
                 draw_line(0,zyf,xM,zyf,foreground_color,0.7f,0xFF00FF00).
  </code></pre>
  
  <p>Why? How to fix it？</p>