libGLESv2: compile entry points in the shared library.

Without this the GN shared library doesn't export any of the gl
entry-points making it useless.

Bug swiftshader:86

Change-Id: I97f6acf4204d6e908ad12c89c79d40769dc824a4
Reviewed-on: https://swiftshader-review.googlesource.com/13308
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>

src/OpenGL/libGLESv2/libGLESv2.vcxproj

diff --git a/src/OpenGL/libGLESv2/libGLESv2.vcxproj b/src/OpenGL/libGLESv2/libGLESv2.vcxproj
index 4f3baaf..8968f0b 100644
--- a/src/OpenGL/libGLESv2/libGLESv2.vcxproj
+++ b/src/OpenGL/libGLESv2/libGLESv2.vcxproj
@@ -344,6 +344,7 @@
     <ClCompile Include="Context.cpp" />

     <ClCompile Include="..\common\debug.cpp" />

     <ClCompile Include="Device.cpp" />

+    <ClCompile Include="entry_points.cpp" />

     <ClCompile Include="Fence.cpp" />

     <ClCompile Include="Framebuffer.cpp" />

     <ClCompile Include="IndexDataManager.cpp" />