if .ext/rdoc exists, ruby/rdoc sometimes crashes

[lsansonetti@…]

Typical backtrace:

#0 0x0096be48 in class_getIvarLayout ()
#1 0x0005aa2d in Auto::MemoryScanner::scan_object_range ()
#2 0x0005ac71 in Auto::MemoryScanner::scan_for_unmarked_blocks ()
#3 0x0005aedb in Auto::MemoryScanner::scan_pending_until_done ()
#4 0x0005b067 in Auto::MemoryScanner::scan ()
#5 0x0004ac3c in Auto::Zone::collect ()
#6 0x0003a788 in auto_collect_internal ()
#7 0x0003b5dd in auto_collect ()
#8 0x001e3aa5 in garbage_collect () at gc.c:1861

Probably a missing write barrier, to investigate.

[lsansonetti@…]

With the recent fixes in trunk, `make install' (and especially the RI generation) should now pass without any problem.