Fix a typo and teach linux code to use data

Fix a typo and teach linux code to use data

Typo: __LINUX__ was used in a conditional code block, while the rest of
      the code uses __linux__

data: free_text_objects(...) #define's 'data' to be 'obj->data' to make
	  the code more compact. The linux-specific parts of the code still
	  used obj->data, which should expand to obj->obj->data, which is
	  wrong.

Signed-off-by: Nikos Ntarmos <ntarmos@cs.uoi.gr>