[LLVMdev] modify cmakefiles to set the default triple of msvc and mingw to i686-pc-mingw

[罗勇刚(Yonggang Luo)]

because on windows platform. i686-pc-winnt is not mature and even
don't working. So the it's better to set it to mingw.
And also those spaces and indent modify is just because of the
original indent is not consistent.
Also, now msvc support multiple target. So it's better to set it as
${LLVM_ALL_TARGETS}
It's can working, why not set it to:.

-- 
         此致
礼
罗勇刚
Yours
    sincerely,
Yonggang Luo