deBOOST: Removing BOOST dependency

[yanyh15]

This is a long term goal. This ticket is used to keep note as we find out how to do that when we go through the refactoring process

1. Replaced BOOST_FOREACH with C++11 range-based "for", see a29d5fc and we will need to do the same in other places where BOOST_FOREACH is used.
2. Some of the BOOST features have become recent C++ standard, e.g. the boost.filesystem library now becomes C++17, we might want to update to use standard C++17, but this will bump the requirement of C++ compiler for compiling. We will need to look into details if we consider doing this.

[yanyh15]

The plan to deBoost can be in two ways:

1. Directly replace with standard C/C++ function if they are available, such as BOOST_FOREACH and boost::filesystem. But since some of the C/C++ features that can directly replace boost are relative new in the C++ standard, e.g. c++17 or c++20, this would bump the compiler requirement for the building. Then if this is not possible now, we will use the second way. We decided to bump the requirement for C++ support to C++17.
   • boost::filesystem
   • BOOST_FOREACH
2. Create wrapper function in src/util for those boost usage in the source tree, such as Rose::FileSystem, and replace those boost usage in other places with Rose::xxx. Then after all the source tree are de-boosted, only dependency on Boost will be in src/util. We will then see whether we need to implemet those boost functions in C++ or not.
   • boost::replace_all_copy ==> Rose::StringUtility::replaceAllCopy

The branch https://github.com/passlab/rexompiler/tree/deBoost is used for this issue. @pflynn157 please update this notes to record what boost features we removed.