Include <sys/resource.h> in dalvik_system_Zygote.cpp

Inclusion of sys/resource.h is needed for getrlimit definition when compiling
with gcc 4.8. Without this include compilation fails:

dalvik/vm/native/dalvik_system_Zygote.cpp: In function ‘int setrlimitsFromArray(ArrayObject*)’:
dalvik/vm/native/dalvik_system_Zygote.cpp:213:19: error: aggregate ‘setrlimitsFromArray(ArrayObject*)::rlimit rlim’ has incomplete type and cannot be defined
     struct rlimit rlim;
                   ^
dalvik/vm/native/dalvik_system_Zygote.cpp:236:43: error: ‘setrlimit’ was not declared in this scope
         err = setrlimit(contents[0], &rlim);
                                           ^

Change-Id: Ic737c78a26cd1fc2187a7a505ae36ec054e4774a
Signed-off-by: Adam Tkac <vonsch@gmail.com>
Dalvik: Better compatibility with different compilers

This fixes building with clang 3.4, and possibly future versions of gcc:
- Don't error out on unused functions generated by gen-mterp.py
  even when we're using -Werror
- Eliminate some dead code (Word/kWordSize definition) clang warns about

Change-Id: I2874c6f05186721636518e422b0f39a3d8e731cd
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>