limits.h relies on PAGE_SIZE being defined without actually including
page.h. Make sure this is included to avoid compilation failures.
Signed-off-by: Arun Raghavan <arun.raghavan@collabora.co.uk>
Also add missing declarations to misc. functions.
Fix clearerr() implementation (previous was broken).
Handle feature test macros like _POSIX_C_SOURCE properly.
Change-Id: Icdc973a6b9d550a166fc2545f727ea837fe800c4
