hg: jdk/submit: 8199405: Bump lowest supported gcc to 4.8

[magnus.ihse.bursie at oracle.com]

Changeset: a19a6228cdb2
Author:    ihse
Date:      2018-03-09 19:12 +0100
URL:       http://hg.openjdk.java.net/jdk/submit/rev/a19a6228cdb2

8199405: Bump lowest supported gcc to 4.8
Reviewed-by: erikj

! make/autoconf/flags-cflags.m4
! make/autoconf/toolchain.m4