glBufferSubData Interface to
OpenGL function glBufferSubData
usage: glBufferSubData( target, vbooffset, datasize, data )
C function: void glBufferSubData(GLenum target, GLint vbooffset, GLsizei datasize, const GLvoid* data)
Psychtoolbox/PsychOpenGL/MOGL/wrap/glBufferSubData.m