Fix unused warning for printf's stdout_putf()

fix gcc warnings

work-around gcc 4.9 demotion to signed

let gcc warn when printf params types don't match format

set explicit C linkage

add snprintf/vsnprintf/vsprintf + tests

test that tinyprintf compiles with various TINYPRINTF_* combinations

allow to selectively compile-in printf/sprintf

rename printf.* -> tinyprintf.*

moving tests to new test/ subdir

remove pointless test

add doc specific to tfp_format

update doc for long long + size_t support

Merge github.com:nmlgc/tinyprintf

add support for z (size_t) modifier