build: Add globbing to conditional targets

Signed-off-by: Pawel Dziepak <pdziepak@quarnos.org>
libstd: Add isalpha()

Signed-off-by: Pawel Dziepak <pdziepak@quarnos.org>
libstd: Add strtoul()

Signed-off-by: Pawel Dziepak <pdziepak@quarnos.org>
libstd: vsnprintf: Fix signed/unsigned casts

Signed-off-by: Pawel Dziepak <pdziepak@quarnos.org>