[PATCH v4 4/6, Committed] [MIPS] Add Loongson 3A1000 processor support

[Gerald Pfeifer]

Hi Paul and Matthew,

I believe it would be good to get this and other MIPS changes covered
in the GCC 9 release notes at https://gcc.gnu.org/gcc-9/changes.html .

Gerald

PS: https://gcc.gnu.org/about.html has background how to go about this.