i#46: Use os_open to parse /proc/cpuinfo instead of fopen.
i#46: Use os_open to parse /proc/cpuinfo instead of fopen.

On error, return a frequency of 1 GHz instead of 1 MHz as was done
previously.

Review URL: https://codereview.appspot.com/6356083

git-svn-id: ed337ca7cdb08c0ba29d8fe58632bb7686892c2d@1455 49cc7528-f6fd-11dd-9d1a-b59b2e1864b6

rnk/dynamorio,rnk/dynamorio,rnk/dynamorio,rnk/dynamorio,rnk/dynamorio