Move the compiler back to 4.8.1 + more small fixes

Summary:
1. Moved the compiler back to 4.8.1 and uses Centos 5.2 binaries if OS is Centos 5.2.

2. Fixes this issue: https://github.com/facebook/rocksdb/issues/7

3. We use lot of c++11 features, so we can't pretend we can compile without them. Makes it a first class dependency.

4. Fix blob_store_test, which failes on Ubuntu with "too many files opened" error

5. Removed dependency on port/port_chromium.h, which does not even exist on our system

Test Plan: make clean; make check

Reviewers: dhruba, kailiu

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14145