* write.c (fixup_segment) [TC_DONT_FIX_NON_ADJUSTABLE]: Use

* write.c (fixup_segment) [TC_DONT_FIX_NON_ADJUSTABLE]: Use
obj_fix_adjustable() and tc_fix_adjustable() to tell whether to
add a symbol's address.  Removed all target-specific #ifdefs that
used to accomplished the same.
* config/tc-v850.h (TC_DONT_FIX_NON_ADJUSTABLE): Define.
* config/tc-m68k.h (TC_DONT_FIX_NON_ADJUSTABLE): Define.
* config/tc-arm.h (TC_DONT_FIX_NON_ADJUSTABLE): Define.
* config/tc-i960.h (TC_DONT_FIX_NON_ADJUSTABLE): Define.
* config/tc-i386.h (TC_DONT_FIX_NON_ADJUSTABLE): Define.