Add /usr/local/include to c_cpp_properties.json's default list of include paths

[waldyrious]

Currently the "includePath" key in c_cpp_properties.json only contains the "/usr/include" path. IMO it would be a good default to also add "/usr/local/include" to it.

[bobbrow]

In the more recent versions of the extension, /usr/local/include is added to the includePath when a new c_cpp_properties.json file is created. Thank you for the suggestion.