* configure.in: Check for lwpid_t, psaddr_t, prgregset_t and
prfpregset_t in <sys/procfs.h>.
* config.in: Add HAVE_LWPID_T, HAVE_PSADDR_T, HAVE_PRGREGSET_T,
HAVE_PRFPREGSET_T.
* gdb_proc_service.h: Only provide typedefs for lwpid_t, psaddr_t,
prgregset_t and prfpregset_t if they are not already present.