etc.c: small cleanup (delete unused functions)

mrb_data_object_alloc: unnecessary cast
mrb_lastline_get: mruby doesn't support $_, weird and unused code
mrb_exec_recursive: see 4e46abb86914b36e70b5f3ad0826d0b648e9b4ef
mrb_block_proc: unused, doesn't really do anything (or needs to be
rewritten)
mrb_obj_to_sym: actually use id (and MSVC detected unreachable code)
Happy new year! (update copyright year)

Let's not wait until May this time
(f0a9b95af3d542ac1db7fcb4a3d77990a284c185)!
clean up external symbols

remove unused and unneeded:
- sysexit_status
- type (a global variable)

add mrb_ prefix to:
- codedump_all
- class_instance_method_list
- parser_dump

make various functions static, incl.:
- yyparse
- make_exception
reindent parse.y
Merge pull request #1668 from cremno/etc-c-cleanup

etc.c: small cleanup
Merge pull request #1669 from cremno/copyright-2014

update copyright year
Merge pull request #1671 from cremno/extern-cleanup

clean up external symbols
remove conflict