zz40-xc-ovr.m4: fix 'wc' detection - follow-up

- Take into account that 'wc' may return leading spaces and/or tabs.

- Set initial IFS to space, tab and newline.

m4/zz40-xc-ovr.m4

@@ -51,10 +51,18 @@ XC_CONFIGURE_PREAMBLE_VER_MINOR  ##
 xc_configure_preamble_ver_major='XC_CONFIGURE_PREAMBLE_VER_MAJOR'
 xc_configure_preamble_ver_minor='XC_CONFIGURE_PREAMBLE_VER_MINOR'
 
-xc_configure_preamble_prev_IFS=$IFS
+#
+# Set IFS to space, tab and newline.
+#
+
+xc_space=' '
+xc_tab='	'
+xc_newline='
+'
+IFS="$xc_space$xc_tab$xc_newline"
 
 #
-# Set internationalization behavior variables
+# Set internationalization behavior variables.
 #
 
 LANG='C'
@@ -64,6 +72,10 @@ export LANG
 export LC_ALL
 export LANGUAGE
 
+#
+# Some useful variables.
+#
+
 xc_msg_warn='configure: WARNING:'
 xc_msg_abrt='Can not continue.'
 xc_msg_err='configure: error:'
@@ -263,9 +275,9 @@ AC_REQUIRE([_XC_CFG_PRE_BASIC_CHK_VAR_PATH])dnl
 # Verify that 'tr' utility is found within 'PATH', otherwise abort.
 #
 
-xc_tst_str='98s7u6c5c4e3s2s10'
+xc_tst_str='${xc_tab}98s7u6c5c4e3s2s10'
 xc_tst_str=`echo "$xc_tst_str" 2>/dev/null \
-  | tr -d '0123456789' 2>/dev/null`
+  | tr -d "0123456789$xc_tab" 2>/dev/null`
 case "x$xc_tst_str" in @%:@ ((
   xsuccess)
     :
@@ -294,7 +306,7 @@ AC_REQUIRE([_XC_CFG_PRE_BASIC_CHK_UTIL_TR])dnl
 
 xc_tst_str='unknown unknown unknown unknown'
 xc_tst_str=`echo "$xc_tst_str" 2>/dev/null \
-  | wc -w 2>/dev/null | tr -d ' ' 2>/dev/null`
+  | wc -w 2>/dev/null | tr -d "$xc_space$xc_tab" 2>/dev/null`
 case "x$xc_tst_str" in @%:@ ((
   x4)
     :
@@ -322,7 +334,8 @@ AC_REQUIRE([_XC_CFG_PRE_BASIC_CHK_UTIL_WC])dnl
 #
 
 xc_tst_str='unknown'
-xc_tst_str=`cat <<_EOT 2>/dev/null | wc -l 2>/dev/null | tr -d ' ' 2>/dev/null
+xc_tst_str=`cat <<_EOT 2>/dev/null \
+  | wc -l 2>/dev/null | tr -d "$xc_space$xc_tab" 2>/dev/null
 unknown
 unknown
 unknown
@@ -425,8 +438,7 @@ AC_REQUIRE([_XC_CFG_PRE_BASIC_CHK_UTIL_TR])dnl
 AC_REQUIRE([_XC_CFG_PRE_BASIC_CHK_UTIL_WC])dnl
 AC_REQUIRE([_XC_CFG_PRE_BASIC_CHK_UTIL_CAT])dnl
 AC_REQUIRE([_XC_CFG_PRE_CHECK_PATH_SEPARATOR])dnl
-IFS=$xc_configure_preamble_prev_IFS
-
+dnl
 xc_configure_preamble_result='yes'
 ])