Limiting dependency Boost libraries

Subject: Limiting dependency Boost libraries
From: Mateusz Loskot (mateusz_at_[hidden])
Date: 2018-06-22 18:13:25

Hi,

(Post-The Grand Merge ideas)

The depinst.py below calculates maximum set of Boost libraries
which are requirements of GIL:

```
$ cd boost_root
$ python tools/boostdep/depinst/depinst.py -v gil | grep dependency
Adding dependency config
Adding dependency core
Adding dependency mpl
Adding dependency iterator
Adding dependency integer
Adding dependency type_traits
Adding dependency concept_check
Adding dependency static_assert
Adding dependency bind
Adding dependency preprocessor
Adding dependency function
Adding dependency lexical_cast
Adding dependency smart_ptr
Adding dependency array
Adding dependency lambda
Adding dependency numeric/conversion
Adding dependency algorithm
Adding dependency filesystem
Adding dependency test
Adding dependency crc
```

The depinst.py does
- only scan GIL headers
- not analyse conditional #include-s, so for some compilation
  cases, some dependencies may not be required.

Since GIL switched to C++11, some may be obvious candidates to get rid of.

Could we brainstorm some priority list of dependencies?
- trivial to remove
- non-trivial to remove
- impossible to removed

Shall we open GH issue for this?

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net