If we bump the lowest supported version of gcc from 4.7 to 4.8, we can remove several checks in the configure script.
Bug: https://bugs.openjdk.java.net/browse/JDK-8199405 WebRev: http://cr.openjdk.java.net/~ihse/JDK-8199405-bump-gcc-to-v4_8/webrev.01 /Magnus
