cc/gcc: add option to enable/disable libmudflap

For some scenarii, libmudflap is not very usefull
or can break the build. Make in an optioon that
defaults to 'N' to be on the safe side.

For the core gcc-s, there is absolutely no need
to build libmidflap.

Idea from: Bernhard Pfund <bernhard@chapter7.ch>

# ia64 specific config options

# depends on EXPERIMENTAL

config ARCH_ia64

    select ARCH_SUPPORTS_64

    select ARCH_DEFAULT_64

    select ARCH_USE_MMU

    select ARCH_SUPPORTS_BOTH_ENDIAN

    help

      The ia64 architecture, as defined by:

        http://www.intel.com/design/itanium/arch_spec.htm