C++ Maps from YAML

• Uses libyaml instead of yaml-cpp for the sake of C++98 compliance. I'm stuck with a compiler that doesn't support C++11.
• Creates a C++ map of vectors of strings out of the contents of the YAML file.
• Uses libyaml's document-based parsing syntax.
• Does not support nested YAML mappings. This is intended only for very simple YAML files.
• Mapping keys are stored as vectors whether they are written as sequences or scalars in the YAML.
• Since all values are strings, they must be manually converted to the correct types.

e.g.

Input YAML (yaml.config)

opt1: true
opt2: false
atoms: [4,3,5]
num: 3.5 
name: "myname"

Output map in C++

atoms: ["4", "3", "5", ]
name: ["myname", ]
num: ["3.5", ]
opt1: ["true", ]
opt2: ["false", ]

You'll probably need to modify the Makefile to point to the PREFIX where libyaml is installed.

Based on advice from:

• https://stackoverflow.com/questions/36410122/c-libyaml-document-based-parsing
• http://staskobzar.blogspot.com/2017/04/yaml-documents-parsing-with-libyaml-in-c.html
• https://www.wpsoftware.net/andrew/pages/libyaml.html