lib: Add file_cache_new_path() to include path in error messages.

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Made file_cache_set_size() public. --HG-- branch : HEAD

deinit, unref, destroy, close, free, etc. functions now take a pointer to their data pointer, and set it to NULL. This makes double-frees less likely to cause security holes. --HG-- branch : HEAD

s/occured/occurred/ --HG-- branch : HEAD

Added file_cache_write() to update cached memory area. --HG-- branch : HEAD

Changed file_cache_invalidate()'s size argument to uoff_t type. --HG-- branch : HEAD

Cache file works now with mmap_disable=yes. Still needs a few optimizations. --HG-- branch : HEAD