_exports.h: reorganize a bit

_exports.h: reorganize a bit

The current list of exported functions is somewhat of a
mess. Reorganize them so that related functionality is kept together:

- console I/O: move vprintf next to printf and the getc/putc functions

- integer parsing: move the *strto* functions together

- standard string.h stuff: move memset() and strcpy() next to strcmp()

- time: move mdelay() next to udelay() and get_timer()

Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
Reviewed-by: Tom Rini <trini@konsulko.com>