exec: Use fprintf_function for dump_exec_info (format checking)

fprintf_function uses format checking with GCC_FMT_ATTR.

It is declared in qemu-common.h and used in cpu-all.h
(which is included from cpu.h), so qemu-common.h must
be included earlier. Some redundant include statements
for standard include files were removed.

Fix also two format errors (ptrdiff_t needs %td).

Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
