Review and update bin/cdt-* executable help information and man pages.

[ScottBailey]

cdt-cpp --help has a few issues. It seems worthwhile to review and correct this text. While we are at it, it seems useful to review all the cdt tools: cdt-abidiff cdt-cc cdt-cpp cdt-init cdt-ld.

Here are some cpp-cdt problem examples:

• OVERVIEW: cdt-cpp (Eosio C++ -> WebAssembly compiler) Should Eosio be replaced by AntelopeIO?
• inconsistent termination: some help ends with a period while some does not
• -O=<string> - Optimization level s, 0-3 - string could/should be s or something else? What about -O3? Is that valid? Evaluate this --flag=<string> for all similar options.
• is --fnative always x86_64?

[stephenpdeos]

More conversation within #121

[dimas1185]

most of points of a little to no value