ARM: use <target/arm.h> not armv4_5.h

ARM: use <target/arm.h> not armv4_5.h

Move most declarations in <target/armv4_5.h> to <target/arm.h>
and update users.

What's left in the older file is stuff that I think should be
removed ... the old register cache access stuff, which makes it
awkward to support microcontroller profile (Cortex-M) cores.

The armv4_5_run_algorithm() declaration was moved too, even
though it's not yet as generic as it probably ought to be.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>