Reimport mbchk.

* util/Makefile.am: New file.
	* util/mbchk.c: Likewise.
	* Makefile.am (SUBDIRS): Add util.
	* configure.ac: New options --enable-mbchk. Check for HELP2MAN.
	(CFLAGS): Don't alter.
	(COND_MAN_PAGES): New conditional.
	(AC_CONFIG_FILES): Add util/Makefile.
	* doc/Makefile.am (kernel_CFLAGS): Add -m32 and -nostdlib.
	* doc/multiboot.texi (Invoking mbchk): New chapter.

util/Makefile.am

@@ -0,0 +1,17 @@
+
+HELP2MAN = @HELP2MAN@
+if COND_MAN_PAGES
+man_MANS = mbchk.1
+endif
+
+if BUILD_MBCHK
+bin_PROGRAMS = mbchk
+endif
+
+mbchk_SOURCES = mbchk.c
+mbchk_CPPFLAGS = -I$(top_srcdir)/doc 
+
+$(srcdir)/mbchk.1: ./mbchk
+	$(HELP2MAN)  \
+		--name="check the format of a Multiboot kernel" \
+		--section=1 --output=$@ ./$<