code/arm-vm: added alien type OS-CONTEXT-T
compiler/arm/move: replaced mov by load-immediate-word

not all allowed values fit into an ARM immediate
src/compiler/arm/arith: added various VOPs

  - added modular fun LOGNOT-MOD32
  - added translation VOPs
    LOGNOT-MOD32/UNSIGNED=>UNSIGNED
    BIGNUM-LENGTH
    BIGNUM-SET-LENGTH
    BIGNUM-REF
    BIGNUM-SET
    ADD-W/CARRY
    SUB-W/BORROW
    BIGNUM-MULT
    BIGNUM-LOGNOT
    BIGNUM-FLOOR
    DIGIT-ASHR
    DIGIT-LSHR
    DIGIT-ASHL
    all but BIGNUM-FLOOR adjusted versions from MIPS
    BIGNUM-FLOOR is a version from SPARC that needs only 5 instead of 7 unsigned-reg registers.
  - added translation VOPs
    FAST-NEGATE/FIXNUM: SPARC
    FAST-NEGATE/SIGNED: SPARC
    FAST-LOGNOT/FIXNUM: SPARC
    FAST-LOGNOT/SIGNED: SPARC
    FAST-LOGNOR/FIXNUM=>FIXNUM: MIPS
    UNSIGNED-BYTE-32-COUNT: MIPS
    SIGNED-BYTE-32-LEN: MIPS
    FAST-ASH-LEFT/FIXNUM=>FIXNUM: MIPS
    FAST-ASH-LEFT/SIGNED=>SIGNED: MIPS
    FAST-ASH-LEFT/UNSIGNED=>UNSIGNED: MIPS
    FAST-ASH/UNSIGNED-UNSIGNED: MIPS
    FAST-ASH/SIGNED-SIGNED: MIPS
  - added source transform LOGNAND: MIPS
removed float related things using #!-arm
added translate VOPs CHAR-CODE and CODE-CHAR, adjusted from SPARC
src/compiler/arm/sap: split POINTER+-C into POINTER+-UNSIGNED-C and POINTER+-SIGNED-C

the reason is, that ARM does not like negative immediates
removed float related things using #!-arm
removed float related things using #!-arm
that conditional should be better