message: Allow NULL in glClear*Buffer and glClear*Tex functions
  * The spec says that if data is NULL, it acts like a buffer filled with
  zeroes, so we can just memset.
diff: @@ -3577,7 +3577,10 @@ bool WrappedOpenGL::Serialise_glClearNamedBufferDataEXT(SerialiserType &ser, GLu
  case eGL_UNSIGNED_INT_10_10_10_2:
  case eGL_UNSIGNED_INT_2_10_10_10_REV: s = 4; break;
  }
  + if(dataPtr)
  memcpy(data, dataPtr, s);
  + else
  + memset(data, 0, s);
  }
  SERIALISE_ELEMENT(data);
  @@ -3716,7 +3719,10 @@ bool WrappedOpenGL::Serialise_glClearNamedBufferSubDataEXT(SerialiserType &ser,
  case eGL_UNSIGNED_INT_10_10_10_2:
  case eGL_UNSIGNED_INT_2_10_10_10_REV: s = 4; break;
  }
  + if(dataPtr)
  memcpy(data, dataPtr, s);
  + else
  + memset(data, 0, s);
  }
  SERIALISE_ELEMENT(data);
  @@ -4014,7 +4020,10 @@ bool WrappedOpenGL::Serialise_glClearTexImage(SerialiserType &ser, GLuint textur
  case eGL_UNSIGNED_INT_10_10_10_2:
  case eGL_UNSIGNED_INT_2_10_10_10_REV: s = 4; break;
  }
  + if(dataPtr)
  memcpy(data, dataPtr, s);
  + else
  + memset(data, 0, s);
  }
  SERIALISE_ELEMENT(data);
  @@ -4124,7 +4133,10 @@ bool WrappedOpenGL::Serialise_glClearTexSubImage(SerialiserType &ser, GLuint tex
  case eGL_UNSIGNED_INT_10_10_10_2:
  case eGL_UNSIGNED_INT_2_10_10_10_REV: s = 4; break;
  }
  + if(dataPtr)
  memcpy(data, dataPtr, s);
  + else
  + memset(data, 0, s);
  }
  SERIALISE_ELEMENT(data);
  