gcc/testsuite:
* gcc.dg/c90-float-1.c: Also test that C1X macros are not defined.
* gcc.dg/c99-float-1.c: Also test that C1X macros are not defined.
* gcc.dg/c1x-float-1.c: New test.
libcpp:
* include/cpplib.h (enum c_lang): Add CLK_GNUC1X and CLK_STDC1X.
* init.c (lang_defaults): Add entries for new language variants.
(cpp_init_builtins): Define __STDC_VERSION__ to 201000L for C1X
variants.