Use GCC's __attribute__((const)) to reduce code size

__attribute__((const)) is mainly intended for the compiler to optimize
away repeated calls to a function that the compiler knows will return
the same value repeatedly.

By adding __attribute__((const)), the compiler can choose to call the
function just once and cache the return value.  Therefore, this yields
code size reduction.

Here are the reference results by arm-eabi-size for crespo device:

[before]
   text    data     bss     dec     hex filename
 267715   10132   45948  323795   4f0d3

[after]
   text    data     bss     dec     hex filename
 267387   10132   45948  323467   4ef8b

Change-Id: I1d80465c0f88158449702d4dc6398a130eb77195
getopt(): fix missing carriage return on bad parameters

This affect all command line tools which show the usage on stdout
after an invalid parameter error (printed on stderr)

Change-Id: I8e2cb3fda241ab989dc42055f15082f8b3ba1397
Signed-off-by: Tanguy Pruvot <tanguy.pruvot@gmail.com>
headers: Unbreak some ARM syscalls

Restore the outside-kernel exclusion for some syscalls that was
removed by change I959b64280e184655ef8c713aa79f9e23cb1f7df4,
since these syscalls are used elsewhere.

Change-Id: I5b5bf3d78edd137e820d25281a375966b6c009ec
armv6: REX routines are currently broken, use alternatives

Change-Id: I7ac05ab6add7802a4cc24fe36f7181e7cdfe07e0