* as.h (enum _relax_state): Add rs_leb128.

    * as.h (enum _relax_state): Add rs_leb128.
        * read.c (potable): Add sleb128 and uleb128.
        (sizeof_*leb128, output_*leb128, emit_leb128_expr, s_leb128): New
        functions.
        * read.h: Update prototypes.
        * symbols.c (resolve_symbol_value): Streamline quite a bit.  Return
        the symbol value, add a second FINALIZE argument that prevents
        changes from being comitted.  Update all callers.
        * write.c (cvt_frag_to_fill, relax_segment): Handle rs_leb128.
        * doc/as.texinfo: Document the new pseudos.