Add json_map and json_set buildfile value types

These expose the std::map<json_value,json_value> and std::set<json_value>
types to buildfiles.

New functions:

  $size(<json-set>)
  $size(<json-map>)
  $keys(<json-map>)

Note that the $keys() function returns the list of map key as a json array.

For example:

m = [json_map] 2@([json] a@1 b@2) 1@([json] 1 2)
s = [json_set] ([json] x@1 y@2) ([json] a@1 b@2)

print ($m[2][b])              # 2
print ($s[([json] y@2 x@1)])  # true

0 files changed, 0 insertions, 0 deletions