+ added voglreplay to the list of things we build on windows.
- Added custom build step on voglcore to copy DLLs (particularly pthreads) to runtime directory
- temporarily relaxed restrictions in change_pointer_sizes
- added VOGL_PLATFORM_HAS_X11 which tells us if (duh?) the platform supports X11.
- removed defunct plat_getppid()
- added PLAT_RTLD_LAZY
- added plat_load_system_gl to load system GL and return it.
- Windows now supports dumping traces from binary to json via voglreplay
- wglGetProcAddress now properly dumps the string requested on windows.
- For windows, re-get function pointers after MakeCurrent.
- unified vogl_get_proc_address_helper_return_wrapper between platforms