i#1551 Port DynamoRIO to ARM: split arch/proc.c
- move core/arch/proc.c to core/arch/x86/proc.c
- extract common code from proc.c to core/arch/proc_shared.c
- add core/arch/arm/proc.c

R=bruening@google.com
BUG=1551

Review URL: https://codereview.appspot.com/180200043

git-svn-id: https://dynamorio.googlecode.com/svn/trunk@3024 49cc7528-f6fd-11dd-9d1a-b59b2e1864b6