This patch fixes PR 58944

This patch fixes PR 58944
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58944

ix86_valid_target_attribute_tree in config/i386/i386.c was
refactored to not depend on global_options structure and to be able to
use any gcc_options structure.  One clean way to fix this is by having
target_option_default_node save all the default target options which
can be restored to any gcc_options structure. The root cause of the
above bugs was that ix86_arch_string and ix86_tune_string was not
saved in target_option_deault_node.

This patch saves all the  target options used in i386.opt which are
either obtained from the command-line or set to some default.

Testing:
Patch tested for bootstrap on all default languages(also obj-c++ and ada)
on x86_64 and regression testsuite checked for parity with RUNTESTFLAGS -m32
and m64.

From-SVN: r205616