autoconf: Fix build on host.

Host C library does not have stdatomic.h but no macro it set to reflect
this.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
atomic: Add basic doxygen comments.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
benchmark: Provide module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
bitops: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
enum: Module and data structure documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
fuzz: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
hex: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
list: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
messageq: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
pack: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
protothreads: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
rand: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
string: Migrate the strdup_printf functions to string library.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
string: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
time: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
util: Module and partial function documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
wavheader: Module documentation.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>
gitignore: Hide update_docs.sh

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>