jslint src/api.js - replace expression "xxx == null" with "isNullOrUndefined(xxx)"

jslint src/api.js - replace expression "void 0" with "undefined"
jslint src/api.js - fix warning "Line is longer than 80 characters."
jslint src/api.js - fix warning "Undeclared xxx."
jslint src/api.js - fix miscellaneous jslint warnings in src/api.js
jslint - allow jslint to print all warnings
jslint - ignore warning subscript_a

Author: kai.zhu