* Add sourcemap examples for identifiers in code generator.
* Generate sourcemaps with exact mappings for identifiers, even if leading/trailing tokens also use that location.
Exposes raw mappings when source map generation is enabled. To avoid the cost of source map generation for consumers of the raw mappings only, `.map` is changed to a getter that generates the source map lazily on first access.
Rather than repeating the original location when we exit a node, we need to restore the previous parent’s original line location, since the source map format denotes the start location.
Removed `@flow` annotation from files that don't actually pass Flow check at the moment. These will be added back file by file once the files are properly converted to use Flow.
Closes#3064
