README: update example with improved macro

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
consolidate message printing into _TAP_VPRINT_MSG

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
add basic sanity test

Verifies that the library compiles with relatively strict compiler
flags.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
10-basic.c: replace fileno with macros

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>