vmem: make sure a pool is destroyed

Make sure that a destroyed pool cannot be reused.

Ref: pmem/issues#20
Merge pull request #90 from ldorau/vmem-destroy-pool_id-in-pool_destroy

vmem: make sure a pool is destroyed
vmem: remove unnecessary assert in vmem_free()
Merge pull request #91 from krzycz/vmem-null_free

vmem: remove unnecessary assert in vmem_free()
common: fix run tests by superuser
vmem: fix dependencies on jemalloc library

Automatically rebuild libjemalloc and libvmem in case of any change
in jemalloc source code.
Merge pull request #94 from krzycz/vmem-jemalloc_dep

vmem: fix dependencies on jemalloc library
common: link to libpthread
Merge pull request #93 from spawlows/common-util-fix-tests-by-root

common: fix run tests by superuser
Merge pull request #92 from krzycz/common-libpthread

common: link to libpthread