exec.h cleanup

Move softmmu_exec.h include directives from target-*/exec.h to
target-*/op_helper.c. Move also various other stuff only used in
op_helper.c there.

Define global env in dyngen-exec.h.

For i386, move wrappers for segment and FPU helpers from user-exec.c
to op_helper.c. Implement raise_exception_err_env() to handle dynamic
CPUState. Move the function declarations to cpu.h since they can be
used outside of op_helper.c context.

LM32, s390x, UniCore32: remove unused cpu_halted(), regs_to_env() and
env_to_regs().

ARM: make raise_exception() static.

Convert
#include "exec.h"
to
#include "cpu.h"
#include "dyngen-exec.h"
and remove now unused target-*/exec.h.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

dyngen-exec.h

@@ -64,6 +64,8 @@ typedef void * host_reg_t;
 #error unsupported CPU
 #endif
 
+register CPUState *env asm(AREG0);
+
 #define xglue(x, y) x ## y
 #define glue(x, y) xglue(x, y)
 #define stringify(s)	tostring(s)