Change print_file to take a prefix and a file descriptor and remove the
buffer argument. Instead allocate a large enough buffer on the stack.
Also, as print_file was immediately followed by a my_fwrite, move the
my_fwrite call into print_file. 
This a sort of a prepatch because we want to use VG_(fdprintf) here
and for that we need to get rid of buffer arithmetic as in 
VG_(sprintf)(outbuf + 4, .....)


git-svn-id: svn://svn.valgrind.org/valgrind/branches/BUF_REMOVAL@14339 a5019735-40e9-0310-863c-91ae7b9d1cf9
I'm attempting to convert dump.c to use VG_(fdprintf). That won't
happen in one large patch but in several smaller ones that can be
proofread. To keep things functional, make my_fwrite unbuffered
(as VG_(fdprintf) is unbuffered). Add a big FIXME so this won't
be forgotten.


git-svn-id: svn://svn.valgrind.org/valgrind/branches/BUF_REMOVAL@14340 a5019735-40e9-0310-863c-91ae7b9d1cf9