Add arm specific configuration to help in the port.
Makefile changes to build on ARM
Add fake cpuid for ARM

TODO: proper implementation using procinfo
arm: use LLVM3.5
Rename Make.inc.arm to ARM.inc
Add checksums for llvm 3.5.0
Add basic ARM README
ARM.inc should have lower precedence than Make.user
Reorganize Make.inc to do detection earlier
add checked_{add,sub,mul} for BigInt
fix #5935 (rationalize returns curious/incorrect values)

Partially addresses #7501.
Merge branch 'arm-make3' of github.com:JuliaLang/julia into arm-make3

Conflicts:
	Make.inc
Update README.arm
arm: don't use system SuiteSparse
Restore the Make.inc to what it was at in a2582d08e1402bcede8c5e023cb26da939a7d2cc
Some FFTW build tweaks.
arm: Revert the changes made to base/constants.jl earlier.
Remove ARM.inc inclusion in Make.inc.
Merge pull request #7662 from JuliaLang/arm-make3

build changes for ARM
Add `no such instruction` troubleshooting notes to README.md