[PATCHv3][ARM] -mpure-code option for ARM

[David Edelsohn]

This patch broke bootstrap.

In file included from
/nasfarm/edelsohn/src/src/gcc/target-def.h:106:0,                 from
/nasfarm/edelsohn/src/src/gcc/config/rs6000/rs6000.c:77:./target-hooks-def.h:92:38:
error: 'hook_uint_uintp_false' was not declared in this scope

 #define TARGET_ASM_ELF_FLAGS_NUMERIC hook_uint_uintp_false
                          ^./target-hooks-def.h:2205:5: note: in
expansion of macro 'TARGET_ASM_ELF_FLAGS_NUMERIC'
TARGET_ASM_ELF_FLAGS_NUMERIC, \

     ^

./target-hooks-def.h:1792:5: note: in expansion of macro 'TARGET_ASM_OUT'

     TARGET_ASM_OUT, \

     ^

/nasfarm/edelsohn/src/src/gcc/config/rs6000/rs6000.c:40709:29: note:
in expansion of macro 'TARGET_INITIALIZER'

 struct gcc_target targetm = TARGET_INITIALIZER;