Fix various typos in doc/README and .html files

Fix various typos in doc/README and .html files
(Cherry-pick commit 6afeb18 from 'master' branch.)

* doc/README.Mac: Fix a typo ("command-line").
* doc/README.amiga: Fix typos ("recommendation", "compiling",
"favorably").
* doc/README.cords: Fix a typo ("and").
* doc/README.macros: Fix a typo ("canceled").
* doc/README.sgi: Fix a typo ("related").
* doc/README.solaris2: Fix a typo ("offset").
* doc/leak.html: Fix a typo ("e.g.").
* doc/overview.html: Fix a typo ("December").
* doc/porting.html: Fix typos ("not supported yet", "signaled",
"not defined yet").
* doc/scale.html: Fix typos ("free", "busy-waiting").
* doc/simple_example.html: Fix a typo ("have not yet").
* tests/test_cpp.cc (main): Fix a typo ("command line") in comment.