i386: Implement asm flag outputs

i386: Implement asm flag outputs

        * config/i386/constraints.md (Bf): New constraint.
        * config/i386/i386-c.c (ix86_target_macros): Define
        __GCC_ASM_FLAG_OUTPUTS__.
        * config/i386/i386.c (ix86_md_asm_adjust): Handle =@cc* constraints
        as flags outputs.
        * doc/extend.texi (FlagOutputOperands): Document them.
testsuite/
        * gcc.target/i386/asm-flag-1.c: New.
        * gcc.target/i386/asm-flag-2.c: New.
        * gcc.target/i386/asm-flag-3.c: New.
        * gcc.target/i386/asm-flag-4.c: New.
        * gcc.target/i386/asm-flag-5.c: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@225122 138bc75d-0d04-0410-961f-82ee72b054a4