Passing a 'call statement' to CHECK_GL_ERROR has various issues.
For once, it confuses code parsers in many editors and other
tools that work with C++ source directly.
Moreover, this can lead to subtle bugs if a mistake is
made with the definition of CHECK_GL_ERROR.
It also causes incorrect warnings if CHECK_GL_ERROR is
used with an "empty" call statement.
svn-id: r51050