#14 feature: add function name_is_nocase

[spy]

there is a function find_nocase but to test a name case independantly we have to do it by hand;
for consistency it would be better to always use the same compare algorithm so I propose to add the followings:
JSONNODE_ITERATOR json_name_is_nocase(JSONNODE * node, json_char * name); // case independant
JSONNODE_ITERATOR json_name_is(JSONNODE * node, json_char * name); // case dependant for completness
this is helper functions and no modification is required to actual source, only some add