Merge branch 'more_skylake_support' into 'master'

Added more CPUID strings to the ax_gcc_archflag.m4 for skylake i7 chips.

Closes #473

See merge request !630

m4/ax_gcc_archflag.m4

@@ -109,7 +109,7 @@ case $host_cpu in
 	    *3?6[[ae]]?:*:*:*) ax_gcc_arch="ivybridge core-avx-i corei7-avx corei7 core2 pentium-m pentium3 pentiumpro" ;;
 	    *3?6[[cf]]?:*:*:*|*4?6[[56]]?:*:*:*) ax_gcc_arch="haswell core-avx2 core-avx-i corei7-avx corei7 core2 pentium-m pentium3 pentiumpro" ;;
 	    *3?6d?:*:*:*|*4?6[[7f]]?:*:*:*|*5?66?:*:*:*) ax_gcc_arch="broadwell core-avx2 core-avx-i corei7-avx corei7 core2 pentium-m pentium3 pentiumpro" ;;
-	    *4?6[[de]]?:*:*:*) ax_gcc_arch="skylake haswell sandybridge core-avx2 core-avx-i corei7-avx corei7 core2 pentium-m pentium3 pentiumpro" ;;	
+	    *4?6[[de]]?:*:*:*|*5?6[[de]]?:*:*:*) ax_gcc_arch="skylake haswell sandybridge core-avx2 core-avx-i corei7-avx corei7 core2 pentium-m pentium3 pentiumpro" ;;	
 	    *5?6[[56]]?:*:*:*) ax_gcc_arch="skylake-avx512 skylake haswell sandybridge core-avx2 core-avx-i corei7-avx corei7 core2 pentium-m pentium3 pentiumpro" ;;	
             *8?6[[de]]?:*:*:*|*9?6[[de]]?:*:*:*) ax_gcc_arch="kabylake skylake broadwell haswell sandybridge core-avx2 core-avx-i corei7-avx corei7 core2 pentium-m pentium3 pentiumpro" ;;
 	    *1?6c?:*:*:*|*2?6[[67]]?:*:*:*|*3?6[[56]]?:*:*:*) ax_gcc_arch="bonnell atom core2 pentium-m pentium3 pentiumpro" ;;