Update fbcode_config.sh to use latest versions automatically

Update fbcode_config.sh to use latest versions automatically

Summary:
Update fbcode_config.sh so that It try to use the latest version for dependencies that we are using, after updating the code these libraries where updated

```
Snappy: 1.0.3 => 1.1.3
GFLAGS: 1.6 => 2.1.1
JEMALLOC: 3.6.0 => 4.0.3
```

I have also updated clang from 3.7 to 3.7.1

```
Clang 3.7 => 3.7.1
```

Another change is that we use the same tp2 directory as fbcode, so we dont need to keep changing commit hash every time we need to change a version of a compiler or a library

Test Plan:
make check -j64
USE_CLANG=1 make check -j64

DISABLE_JEMALLOC=1 OPT=-g make all valgrind_check -j32 (make sure it's running)

Reviewers: yhchiang, anthony, rven, kradhakrishnan, andrewkr, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D53037

(cherry picked from commit 538eec0661e6e66bc54fc189295c342a84ea7f54)