Avoid try, catch, throw and use alloc_construct and alloc_destroy

[glenfe]

This change:

• Uses RAII instead of try, catch, throw to achieve exception safety with or without exceptions enabled
• Uses boost::alloc_construct and boost::alloc_destroy from Boost.Core to simplify the implementation

Note that you don't need to use allocator_traits for allocate() and deallocate(). Every allocator is required to provide them.

[codecov[bot]]

Codecov Report

Merging #190 into develop will decrease coverage by 0.04%. The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop     #190      +/-   ##
===========================================
- Coverage      100%   99.95%   -0.05%     
===========================================
  Files           44       44              
  Lines         2126     2123       -3     
===========================================
- Hits          2126     2122       -4     
- Misses           0        1       +1

Impacted Files	Coverage Δ
include/boost/histogram/detail/variant.hpp	100% <100%> (ø)	:arrow_up:
include/boost/histogram/unlimited_storage.hpp	100% <100%> (ø)	:arrow_up:
include/boost/histogram/detail/large_int.hpp	99.27% <0%> (-0.73%)	:arrow_down:

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[HDembinski]

Beautiful solution, much better than using macros and makes better use of existing library code. Thank you!

[HDembinski]

On 12. May 2019, at 18:43, Glen Fernandes notifications@github.com wrote:

The failure appears to be that Appveyor is using Boost.Core from master instead of Boost.Core from develop. I'll merge Core develop to master later today.

Yes, I need to fix the Appveyor build so that it correctly uses the develop and master branches, as I am doing already in Travis.