Study and possibly utilize new gcc flags

[arbiter0xf]

References:

• https://stackoverflow.com/questions/3375697/what-are-the-useful-gcc-flags-for-c?noredirect=1&lq=1
• https://stackoverflow.com/questions/154630/recommended-gcc-warning-options-for-c
• https://stackoverflow.com/questions/8946797/gcc-options-for-strictest-c-code