Build NetBSD libc library in world in ELF mode.

3 sets of libraries are built now:
  . ack: all libraries that ack can compile (/usr/lib/i386/)
  . clang+elf: all libraries with minix headers (/usr/lib/)
  . clang+elf: all libraries with netbsd headers (/usr/netbsd/)

Once everything can be compiled with netbsd libraries and headers, the
/usr/netbsd hierarchy will be obsolete and its libraries compiled with
netbsd headers will be installed in /usr/lib, and its headers
in /usr/include. (i.e. minix libc and current minix headers set
will be gone.)

To use the NetBSD libc system (libraries + headers) before
it is the default libc, see:
   http://wiki.minix3.org/en/DevelopersGuide/UsingNetBSDCode
This wiki page also documents the maintenance of the patch
files of minix-specific changes to imported NetBSD code.

Changes in this commit:
  . libsys: Add NBSD compilation and create a safe NBSD-based libc.
  . Port rest of libraries (except libddekit) to new header system.
  . Enable compilation of libddekit with new headers.
  . Enable kernel compilation with new headers.
  . Enable drivers compilation with new headers.
  . Port legacy commands to new headers and libc.
  . Port servers to new headers.
  . Add <sys/sigcontext.h> in compat library.
  . Remove dependency file in tree.
  . Enable compilation of common/lib/libc/atomic in libsys
  . Do not generate RCSID strings in libc.
  . Temporarily disable zoneinfo as they are incompatible with NetBSD format
  . obj-nbsd for .gitignore
  . Procfs: use only integer arithmetic. (Antoine Leca)
  . Increase ramdisk size to create NBSD-based images.
  . Remove INCSYMLINKS handling hack.
  . Add nbsd_include/sys/exec_elf.h
  . Enable ELF compilation with NBSD libc.
  . Add 'make nbsdsrc' in tools to download reference NetBSD sources.
  . Automate minix-port.patch creation.
  . Avoid using fstavfs() as it is *extremely* slow and unneeded.
  . Set err() as PRIVATE to avoid name clash with libc.
  . [NBSD] servers/vm: remove compilation warnings.
  . u32 is not a long in NBSD headers.
  . UPDATING info on netbsd hierarchy
  . commands fixes for netbsd libc

commands/reboot/log.c

@@ -55,9 +55,17 @@ void write_log()
   fd = open(WTMP,O_APPEND|O_WRONLY,1);
   if (fd) {
     if (strcmp(prog,"reboot"))
+#ifdef __NBSD_LIBC
+      strcpy (wtmp.ut_name, prog);
+#else
       strcpy (wtmp.ut_user, prog);
+#endif
     else
+#ifdef __NBSD_LIBC
+      strcpy (wtmp.ut_name, "shutdown"); /* last ... */
+#else
       strcpy (wtmp.ut_user, "shutdown"); /* last ... */
+#endif
     strcpy (wtmp.ut_id, "~~");
     strcpy (wtmp.ut_line, "~");
     wtmp.ut_pid = 0;

commands/reboot/shutdown.c

@@ -396,8 +396,14 @@ int crash_check()
   crashed = (lseek(fd, - (off_t) sizeof(last), SEEK_END) == -1
     || read(fd, (void *) &last, sizeof(last)) != sizeof(last)
     || last.ut_line[0] != '~'
+#ifdef __NBSD_LIBC
+    || (strncmp(last.ut_name, "shutdown", sizeof(last.ut_name))
+     && strncmp(last.ut_name, "halt", sizeof(last.ut_name)))
+#else
     || (strncmp(last.ut_user, "shutdown", sizeof(last.ut_user))
-     && strncmp(last.ut_user, "halt", sizeof(last.ut_user))));
+     && strncmp(last.ut_user, "halt", sizeof(last.ut_user)))
+#endif
+    );
   close(fd);
   return crashed;
 }