lib/vfs/mc-vfs/samba/configure can't set the value of SAMBA_CFLAGS
in lib/vfs/mc-vfs/Makefile.am.
The solution: to avoid configuration code duplication, use environment
variables SMBCONFIGDIR and SMBCODEPAGEDIR to set up values of configdir
and codepagedir variables in lib/vfs/mc-vfs/samba/Makefile because
samba configure is child process of main configure.
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>