RFR (S): 8022956: Clang: enable return type warnings on BSD

[Christian Thalinger]

http://cr.openjdk.java.net/~twisti/8022956/webrev/

8022956: Clang: enable return type warnings on BSD
Reviewed-by:

While implementing a new feature I noticed that Clang isn't complaining about wrong return types while Sun Studio does. The reason is that we turned it off. Turning it on only needs one small code change (plus a bunch of fixes for Zero). We probably should do the same on Linux but I don't have a Linux machine with Clang installed available.

make/bsd/makefiles/gcc.make
src/cpu/zero/vm/assembler_zero.cpp
src/cpu/zero/vm/cppInterpreter_zero.cpp
src/cpu/zero/vm/frame_zero.cpp
src/cpu/zero/vm/frame_zero.inline.hpp
src/cpu/zero/vm/icBuffer_zero.cpp
src/cpu/zero/vm/interp_masm_zero.hpp
src/cpu/zero/vm/interpreter_zero.cpp
src/cpu/zero/vm/nativeInst_zero.hpp
src/cpu/zero/vm/register_zero.cpp
src/cpu/zero/vm/relocInfo_zero.cpp
src/cpu/zero/vm/sharedRuntime_zero.cpp
src/cpu/zero/vm/vtableStubs_zero.cpp
src/os_cpu/bsd_x86/vm/os_bsd_x86.cpp
src/os_cpu/bsd_zero/vm/os_bsd_zero.cpp
src/os_cpu/bsd_zero/vm/thread_bsd_zero.hpp