progs/perf: initial set of simple performance test programs

Initial tests include:
  drawoverhead - measure overhead of state changes w.r.t drawing commands
  teximage - measure glTexImage2D() and glTexSubImage2D() speed
  vbo - measure glBufferData() and glBufferSubData() speed
  vertexrate - measure vertex rate for immediate mode, glDrawArrays, VBOs, etc.
9 files changed