dtc: Address an assortment of portability problems

I've recently worked with a FreeBSD developer, getting dtc and libfdt
working on FreeBSD.  This showed up a number of portability problems
in the dtc package which this patch addresses.  Changes are as
follows:

	- the parent_offset and supernode_atdepth_offset testcases
used the glibc extension functions strchrnul() and strndupa().  Those
are removed, using slightly longer coding with standard C functions
instead.

	- some other testcases had a #define _GNU_SOURCE for no
particular reason.  This is removed.

	- run_tests.sh has bash specific constructs removed, and the
interpreter changed to /bin/sh.  This apparently now runs fine on
FreeBSD's /bin/sh, and I've also tested it with both ash and dash.

	- convert-dtsv0-lexer.l has some extra #includes added.  These
must have been included indirectly with Linux and glibc, but aren't on
FreeBSD.

	- the endian handling functions in libfdt_env.h, based on
endian.h and byteswap.h are replaced with some portable open-coded
versions.  Unfortunately, these result in fairly crappy code when
compiled, but as far as I can determine there doesn't seem to be any
POSIX, SUS or de facto standard way of determining endianness at
compile time, nor standard names for byteswapping functions.

	- some more endian handling, from testdata.h using the
problematic endian.h is simply removed, since it wasn't actually being
used anyway.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
8 files changed