Bring IEEE_FLOAT under gdbarch's control.

Bring IEEE_FLOAT under gdbarch's control.
* gdbarch.sh (IEEE_FLOAT): New entry.
* gdbarch.c, gdbarch.h: Regenerated.
* valprint.c (IEEE_FLOAT): Provide a default #definition for this.
(print_floating): Use IEEE_FLOAT as if it were an expression; use
the code specific to IEEE-format numbers whenever the value of
IEEE_FLOAT is non-zero.
* config/a29k/tm-a29k.h, config/alpha/tm-alpha.h,
config/arc/tm-arc.h, config/arm/tm-arm.h, config/fr30/tm-fr30.h,
config/h8300/tm-h8300.h, config/i386/tm-i386.h,
config/i960/tm-i960.h, config/m88k/tm-m88k.h,
config/mips/tm-mips.h, config/pa/tm-hppa.h,
config/sparc/tm-sparc.h, config/delta/tm-delta.h,
config/frv/tm-frv.h (IEEE_FLOAT): For all ports that #define
IEEE_FLOAT, make sure they give it the value (1).