Fix missing tabs in SMakefile.amiga

* SMakefile.amiga (clean, test, gctest, setjmp_t, gc*.lib, setjmp_t):
Fix indentation (replace spaces with tabs).
Expand tabs to spaces in rarely used (ancient) files

* extra/AmigaOS.c: Expand tabs to spaces.
* extra/MacOS.c: Likewise.
* extra/Mac_files/dataend.c: Likewise.
* extra/Mac_files/datastart.c: Likewise.
* extra/symbian.cpp: Likewise.
* cord/cordxtra.c: Likewise.
Fix typos in comments

* blacklst.c: Fix typo ("even though").
* cord/cordbscs.c: Fix typo ("exponentially").
* cord/cordxtra.c: Fix typo ("represented").
* dyn_load.c: Fix typos ("uncollectible", "occurred").
* extra/AmigaOS: Fix typos ("specific", "necessary", "always",
"effectiveness").
* finalize.c: Fix typo ("descendants").
* include/cord.h: Fix typo ("idiosyncrasies").
* include/gc.h: Fix typo ("collectible").
* include/gc_allocator.h: Fix typos ("allocator", "[un]collectible").
* mach_dep.c: Fix typo ("erroneously").
* malloc.c: Fix typos ("[un]collectible", "pointer-free",
"initialization").
* mallocx.c: Fix typos ("largely", "pointer-free", "uncollectible").
* mark.c: Fix typos ("[un]collectible", "even though").
* misc.c: Fix typo ("erroneously").
* os_dep.c: Fix typos ("non-addressable", "happening", "pointer-free").
* tests/test.c: Fix typos ("uncollectible", "reversed").
* tests/test_cpp.cc: Fix typos ("[un]collectible").
* typd_mlc.c: Fix typo ("copyright").
* win32_threads.c: Fix typos ("optimization", "uncollectible").
Update AUTHORS file
Fix more typos in comments and documentation

* alloc.c: Fix typo ("overflow").
* configure.ac: Fix typo ("optimization").
* doc/README.amiga: Fix typos ("also", "specific", "unnecessary").
* doc/README.cords: Fix typos ("descendants", "highlighted").
* ChangeLog: Fix typos ("[un]collectible").
* README.md: Likewise.
* dbg_mlc.c: Likewise.
* doc/README.hp: Likewise.
* doc/README.linux: Likewise.
* doc/gcdescr.html: Likewise.
* doc/gcinterface.html: Likewise.
* include/gc_mark.h: Likewise.
* include/gc_pthread_redirects.h: Likewise.
* include/new_gc_alloc.h: Likewise.
* include/private/dbg_mlc.h: Likewise.
* include/private/gc_pmark.h: Likewise.
* include/private/gc_priv.h: Likewise.
* new_hblk.c: Likewise.
* ChangeLog: Fix typo ("multi-threaded").
* cord/cordxtra.c: Likewise.
* doc/debugging.html: Likewise.
* doc/gcinterface.html: Likewise.
* doc/leak.html: Likewise.
* doc/overview.html: Likewise.
* doc/simple_example.html: Likewise.
* include/gc_mark.h: Likewise.
* include/private/gc_priv.h: Likewise.
* os_dep.c: Likewise.
* ptr_chck.c: Likewise.
* README.md: Fix typo ("pointer-free").
* allchblk.c: Likewise.
* doc/debugging.html: Likewise.
* doc/gcdescr.html: Likewise.