FindJNI: add some new architecture names for mips release 6
Some new mips architectures have been added for mips release 6. MIPS r6 is not full compatible with the pre-R6 releases: it removes some instruction and changes encoding of some.
These new architectures is mipsr6/mipsr6el/mipsn32r6/mipsn32r6el/mips64r6/mips64r6el.