Update INSTALL.txt
Update INSTALL.txt

Add information about installing PAPI on Intel MIC.
Based upon information from Vince Weaver's PAPI MIC support page.
http://www.eece.maine.edu/~vweaver/projects/mic/

pyrovski/papi,arm-hpc/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,pyrovski/papi,arm-hpc/papi,arm-hpc/papi,pyrovski/papi,arm-hpc/papi,pyrovski/papi,arm-hpc/papi