RFR [jdk11]: 8201349: build broken when configured with --with-zlib=bundled on gcc 7.3

[Baesken, Matthias]

Hello, please review this small downport of  8201349 .
Reason is that we run into  warnings as errors, when building  jdk11 on Linux with gcc-7.X  and  with-zlib=bundled .
This adds  the  compiler options

-Wno-unused-function -Wno-implicit-fallthrough

To some compilations e.g. zlib-files   ; these 2 flags are at least supported with gcc-4.7 , gcc-4.8 ,gcc-7 and gcc-8 .



Bug :

https://bugs.openjdk.java.net/browse/JDK-8201349

jdk/jdk webrev :

https://hg.openjdk.java.net/jdk/jdk/rev/c35eac313084


adjusted Jdk11 webrev :

http://cr.openjdk.java.net/~mbaesken/webrevs/8201349.0_jdk11/


Thanks, Matthias