Fix dpl_get() and dpl_copy() for DPL_OPTION_NOALLOC

Both need to pass the length of the caller's buffer to
the backend.
Support storage class in dpl_s3_put() and dpl_s3_copy()
Change storage class keywords to uppercase
Why do we need to include xattr.h twice? Removed attr/xattr.h
Allow <droplet/vfs.h> to be included in a C++ source.
Non void function needs to return value.
typedef flags to unsigned int.

When you typedef dpl_vfile_flag_t and dpl_vfile_t and others to an enum
type it can only be one of the enum values otherwise the compiler will
compain. Currently you can only store one enum type in it and we want to
store an or-ed value.
Add OBS spec file and install includes not in subdir.
added possiblility to not optimize during compile

you can now set
   %define noopt 1

to not optimize during compiletime, and

   %define noopt 0

to do it.
Allow to define a default_behavior_flags in your context.

Up until now the default behaviour flags are hardcoded to
DPL_BEHAVIOR_KEEP_ALIVE | DPL_BEHAVIOR_VIRTUAL_HOSTING in req.c this
allows you to set a default_behavior_flags in your context that will be
used when it non zero.
Quick and dirty attempt to add proxy support.