Subzero: Fix g++ warnings.

Makefile.standalone

 # The following variables will likely need to be modified, depending on where
 # and how you built LLVM & Clang. They can be overridden in a command-line
 # invocation of make, like:
 #
 #   make LLVM_SRC_PATH=<path> LIBCXX_INSTALL_PATH=<path> CLANG_PATH=<path> \
 #        PNACL_BIN_PATH=<path> ...
 #
 
 # LLVM_SRC_PATH is the path to the root of the checked out source code. This
 # directory should contain the configure script, the include/ and lib/
@@ skipping 171 matching lines @@
 LLVM_EXTRA_WARNINGS := -Wcovered-switch-default
 
 # Use g++ to compile, to check for errors/warnings that clang++ might have
 # missed.  It's unlikely to link, unless LLVM was also built with g++, so the
 # compile_only target should be used.  Note: This ifdef section is deliberately
 # placed here instead of with the other ifdef sections, so that its redefinition
 # of CXX/STDLIB_FLAGS/LLVM_EXTRA_WARNINGS follows their normal definitions.
 ifdef GPLUSPLUS
   CXX := CCACHE_CPP2=yes $(CCACHE) g++
   STDLIB_FLAGS :=
-  LLVM_EXTRA_WARNINGS := -Wno-unknown-pragmas -Wno-unused-parameter \
-                         -Wno-comment -Wno-enum-compare -Wno-strict-aliasing \
-                         -Wno-return-type
+  LLVM_EXTRA_WARNINGS := \
+    -Wcast-qual \
+    -Wno-comment \
+    -Wno-long-long \
+    -Wno-maybe-uninitialized \
+    -Wno-missing-field-initializers \
+    -Wno-unused-parameter \
+    -Wwrite-strings
   OBJDIR := $(OBJDIR)+Gplusplus
 endif
 
 BASE_CXXFLAGS := -std=gnu++11 -Wall -Wextra -Werror -fno-rtti \
   -fno-exceptions $(OPTLEVEL) $(ASSERTIONS) -g -pedantic \
   $(LLVM_EXTRA_WARNINGS) $(CXX_EXTRA)
 
 CXXFLAGS := $(LLVM_CXXFLAGS) $(BASE_CXXFLAGS) $(CXX_DEFINES) $(HOST_FLAGS) \
   $(STDLIB_FLAGS)
 SB_CXXFLAGS := $(SB_LLVM_CXXFLAGS) $(BASE_CXXFLAGS) $(SB_CXX_DEFINES)
@@ skipping 308 matching lines @@
         @echo See Subzero size breakdown in bloat/pnacl-sz.bloat.html
 
 docs:
         make -C docs -f Makefile.standalone
 
 clean:
         rm -rf pnacl-sz *.o $(OBJDIR) $(SB_OBJDIR) build/pnacl-sz.bloat.json
 
 clean-all: clean
         rm -rf build/  crosstest/Output/