die when trying to push past allocated rpn stack size
increase rpn stack size for =, < and > by one to prevent invalid writes
Set CLONE_SKIP in OpenGL::Array to 1, not thread safe

This resolves POGL bug #12: https://sourceforge.net/p/pogl/bugs/12/
Fix POD spelling (thanks fsfs)
updated glext.h to include extensions up to OpenGL 4.2 and used it to generate and update further ancillary files
prepared an xs file for addition of functions needed for gltut
added bindings for glGenVertexArrays and glBindVertexArray
updated freeglut to 2.8.0
added glAttachShader, glDeleteShader, glGetShaderiv_p, glGetShaderInfoLog_p
added glutInitContextVersion, glutInitContextFlags, glutInitContextProfile, GLUT_CORE_PROFILE, GLUT_DEBUG
get program iv
added occlusion query capability
added glDrawElementsBaseVertex_c
add GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_FRAMEBUFFER, GL_FRAMEBUFFER_COMPLETE