[here string] uncompatible change on here string function

[尹剑虹]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-redhat-linux-gnu' 
-DCONF_VENDOR='redhat' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -D_GNU_SOURCE -DRECYCLES_PIDS 
-DDEFAULT_PATH_VALUE='/usr/local/bin:/usr/bin'  -O2 -g -pipe -Wall 
-Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions 
-fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches 
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic 
-Wno-parentheses -Wno-format-security
uname output: Linux dhcp-12-238.nay.redhat.com 4.13.9-200.fc26.x86_64 #1 SMP 
Mon Oct 23 13:52:45 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-redhat-linux-gnu

Bash Version: 4.4
Patch Level: 12
Release Status: release

Description:
        The command line to the right of  "<<<"  is no longer cut by IFS

        [yjh@bash4.4 ~]$ var=$(echo -e "foo\t\tbar")
        [yjh@bash4.4 ~]$ read a <<<$var; echo "$a"
        foo             bar

        [yjh@bash4.2 ~]$ var=$(echo -e "foo\t\tbar")
        [yjh@bash4.2 ~]$ read a <<<$str; echo "$a"
        foo bar


Repeat-By:
        see section "Description"