Tests: Make the config.h grep patterns Meson compatible

Now the test scripts detect both

    #define HAVE_DECODER_ARM
    #define HAVE_DECODER_ARM 1

as support for the ARM filter without confusing it with these:

    #define HAVE_DECODER_ARM64
    #define HAVE_DECODER_ARM64 1

Previously only the ones ending with " 1" were accepted for
the macros where this kind of confusion was possible.

This should help with Meson support because Meson's built-in
features produce config.h entries that are either

    #define FOO 1
    #define FOO 0

or:

    #define FOO
    #undef FOO

The former method has a benefit that one can use "#if FOO" and -Wundef
will catch if a #define is missing (for example, it helps catching
typos). But XZ Utils has to use the latter since it has been
convenient with Autoconf's default behavior.[*] While it's easy to
emulate the Autoconf style (#define FOO 1 vs. no #define at all)
in Meson, it results in clumsy code. Thus it's better to change
the few places in the tests where this difference matters.

[*] While most checks in Autoconf default to the second style above,
    a few things use the first style (like AC_CHECK_DECLS). The mix
    of both styles is the most confusing as one has to remember which
    macro needs #ifdef and which #if. Currently HAVE_VISIBILITY is
    only such config.h entry that is 1 or 0. It comes unmodified
    from Gnulib's visibility.m4.

tests/test_compress.sh

@@ -142,9 +142,9 @@ test_xz -4
 test_filter()
 {
 	if test -f ../config.h ; then
-		grep "define HAVE_ENCODER_$1 1" ../config.h > /dev/null \
+		grep "define HAVE_ENCODER_$1[ 1]*\$" ../config.h > /dev/null \
 			|| return
-		grep "define HAVE_DECODER_$1 1" ../config.h > /dev/null \
+		grep "define HAVE_DECODER_$1[ 1]*\$" ../config.h > /dev/null \
 			|| return
 	fi
 	shift

tests/test_files.sh

@@ -39,7 +39,7 @@ EXIT_STATUS=0
 have_feature()
 {
 	test -f ../config.h || return 0
-	grep "define HAVE_$1 1" ../config.h > /dev/null && return 0
+	grep "define HAVE_$1[ 1]*\$" ../config.h > /dev/null && return 0
 	printf '%s: Skipping because HAVE_%s is not enabled\n' "$2" "$1"
 	EXIT_STATUS=77
 	return 1