- Previously the directory hierarchy was not clear regarding to which
  file belong to which part of the project (client or daemon).
  Further, we will have other clients in the future (such as Fuse).
- CMake files now differentiate between include dirs for all targets
  and target specific ones.
- Removed duplicate -pg flag.
- Not listing header files when adding executables or libraries
  is considered bad practice. Note that include_directories() is adding
  include paths to the code while adding all files used for executables
  and libraries provide the context which files belong to each binary.
  When only include_directories() is set, CMake assumes that all files
  belong to a binary (which is not necessarily true). As a result,
  some IDEs may break as the do not support this assumption.

  In general we should almost always favor explicitness over implicitness.

The preload specific cmake files inherits the global flag declarations,
thus it is not necessary to specify again all the flags.
Moreover the only addition made by this declaration is the `-fPIC` flag.
According to the official CMake docs [1], is set automatically for
library target as SHARED. Thus we don't need to set it explicitely.

[1]: https://cmake.org/cmake/help/v3.6/prop_tgt/POSITION_INDEPENDENT_CODE.html

FILE_OFFSET_BITS flag was required for Fuse builds and is a remnant
from previous fs versions. Currently it is not required

Subprojects specific CMakeLists.txt inherits directives from the main cmake file.
Thus it is not necessary to replicate global level directives

since we use the `include_directories(include)` it is not necessary to
explitely specify all the headers file in the source list.

ADA-FS's statfs will fill the struct mostly with rough estimations.
It is not supposed to return accurate data but "some" data for applications to work

The specific version is necessary for local I/O to work.

Added lseek64 syscall and used file flags properly

Marc Vef authored Feb 23, 2018 and Marc Vef committed Mar 02, 2018

Recompile mercury for local I/O to work

Users may use -DCMAKE_CXX_FLAGS_DEBUG to add addition compiler flags for debug mode.

-g -O2 has been replaced with -O3 in all cases.

The file position of a newly created OpenFile
it wasn't set correctly to 0.

See https://xgitlab.cels.anl.gov/sds/margo/issues/40 for reference of the issue.

Through boost::program_option it is possible to specify which are
the mandatory parameter and to print a proper error message in case some
of them is missing.

5.10.2 -> 5.10.3

5.10.2 couldn't be compiled with gcc 7 due to a rocksDB bug [1]

[1]: https://github.com/facebook/rocksdb/issues/3486

The download script can be used to update dependencies source code by
pull the new version and performing a checkout to that version.
Without forcing (-f) the checkout files that have been modified or
patched won't be updated correctly.

Do not force a specific c(++) compiler by setting the
CMAKE_{}_COMPILER variable.
After the c(++) compiler binary has been choosen check if it is the GNU compilear.

In this way we allow the users to specify a GNU compiler under a non
standard path through the CC and CXX envirnoment variable.