mesa: add another missing GLAPIENTRY keyword

NOTE: this is a candidate for the 7.10 branch.

src/mesa/main/blend.c

@@ -447,7 +447,7 @@ _mesa_BlendEquationSeparateEXT( GLenum modeRGB, GLenum modeA )
 /**
  * Set separate blend equations for one color buffer/target.
  */
-void
+void GLAPIENTRY
 _mesa_BlendEquationSeparatei(GLuint buf, GLenum modeRGB, GLenum modeA)
 {
    GET_CURRENT_CONTEXT(ctx);

src/mesa/main/blend.h

@@ -68,7 +68,7 @@ extern void GLAPIENTRY
 _mesa_BlendEquationSeparateEXT( GLenum modeRGB, GLenum modeA );
 
 
-extern void
+extern void GLAPIENTRY
 _mesa_BlendEquationSeparatei(GLuint buf, GLenum modeRGB, GLenum modeA);