Upgrading jemalloc from 3.6.0 to the latest for fbcode+gcc 4.8.1

Summary:
MyRocks is using jemalloc latest version, not 3.6.0.
Combining multiple versions (3.6.0 in RocksDB and latest in MyRocks)
broke some features -- for example, getting SIGSEGV when heap profiling
was enabled.
This diff switches to use jemalloc latest, if
env variable ROCKSDB_FBCODE_BUILD_WITH_481=1 was set.
My understanding is this env was used by MyRocks only so it would be
safe to change.

Test Plan: building MyRocks then verified jemalloc heap profiling worked

Reviewers: igor, rven, yhchiang, jtolmer, maykov, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D43479

build_tools/fbcode_config4.8.1.sh

@@ -35,8 +35,8 @@ GFLAGS_INCLUDE=" -I /mnt/gvfs/third-party2/gflags/1ad047a6e6f6673991918ecadc6708
 GFLAGS_LIBS=" /mnt/gvfs/third-party2/gflags/1ad047a6e6f6673991918ecadc670868205a243a/1.6/gcc-4.8.1-glibc-2.17/c3f970a/lib/libgflags.a"
 
 # location of jemalloc
-JEMALLOC_INCLUDE=" -I /mnt/gvfs/third-party2/jemalloc/c60d854f7824f334195fe7fd34b2bc9057e3c1f9/3.6.0/gcc-4.8.1-glibc-2.17/4d53c6f/include"
-JEMALLOC_LIB=" /mnt/gvfs/third-party2/jemalloc/c60d854f7824f334195fe7fd34b2bc9057e3c1f9/3.6.0/gcc-4.8.1-glibc-2.17/4d53c6f/lib/libjemalloc.a"
+JEMALLOC_INCLUDE=" -I /mnt/gvfs/third-party2/jemalloc/3691c776ac26dd8781e84f8888b6a0fbdbc0a9ed/dev/gcc-4.8.1-glibc-2.17/4d53c6f/include"
+JEMALLOC_LIB="/mnt/gvfs/third-party2/jemalloc/3691c776ac26dd8781e84f8888b6a0fbdbc0a9ed/dev/gcc-4.8.1-glibc-2.17/4d53c6f/lib/libjemalloc.a"
 
 # location of numa
 NUMA_REV=829d10dac0230f99cd7e1778869d2adf3da24b65