Update the documentation to match the current GC implementation

Update the documentation to match the current GC implementation

* README.md: Update the documentation to match the current
implementation of the collector.
* doc/README.Mac: Likewise.
* doc/README.autoconf: Likewise.
* doc/README.darwin: Likewise.
* doc/README.hp: Likewise.
* doc/README.linux: Likewise.
* doc/README.macros: Likewise.
* doc/README.solaris2: Likewise.
* doc/README.win32: Likewise.
* doc/debugging.md: Likewise.
* doc/finalization.md: Likewise.
* doc/gc.man: Likewise.
* doc/gcdescr.md: Likewise.
* doc/gcinterface.md: Likewise.
* doc/leak.md: Likewise.
* doc/overview.md: Likewise.
* doc/porting.md: Likewise.
* doc/scale.md: Likewise.