title: gem install mongoid --platform=ruby failed to build gem native extension
body: <p>i 'm using windows 7 and when i try to install mongoid i have this problem this is the log </p>
  
  <pre><code>C:/Ruby200/bin/ruby.exe -r ./siteconf20140806-7376-tm3b3l.rb extconf.rb
  creating Makefile
  
  make "DESTDIR=" clean
  
  make "DESTDIR="
  generating native-i386-mingw32.def
  compiling native.c
  In file included from c:/Ruby200/include/ruby-2.0.0/ruby/defines.h:153:0,
               from c:/Ruby200/include/ruby-2.0.0/ruby/ruby.h:70,
               from c:/Ruby200/include/ruby-2.0.0/ruby.h:33,
               from native.c:26:
  c:/Ruby200/include/ruby-2.0.0/ruby/win32.h: In function 'rb_w32_pow':
  c:/Ruby200/include/ruby-2.0.0/ruby/win32.h:801:5: warning: implicit declaration of
  function '_controlfp' [-Wimplicit-function-declaration]
  c:/Ruby200/include/ruby-2.0.0/ruby/win32.h:802:16: error: '_PC_64' undeclared (first
  use in this function)
  c:/Ruby200/include/ruby-2.0.0/ruby/win32.h:802:16: note: each undeclared identifier is 
  reported only once for each function it appears in c:/Ruby200/include/ruby- 
  2.0.0/ruby/win32.h:802:24: error: '_MCW_PC' undeclared (first use in this function)
  
  make: *** [native.o] Error 1
  
  make failed, exit code 2
  </code></pre>
  
  <p>i have installed devKit</p>