[NCF-280]/TLO-836022

Fix bug where leading backslash digit
in name was not being properly handled.
The reason was that I accidentally attemped to allow \x... and \0...
escapes in identifiers. This make identifiers
with leading escaped digits not work any more.
Also added test case.
Refactored read_scale(), memio_new(), var_create_dataset() and makespecial()
    to clean up resources properly on failure.

Refactored doubly-linked list code for objects in the libsrc4 directory,
    cleaning up the add/del routines, breaking out the common next/prev
    pointers into a struct and extracting the add/del operations on them,
    changed the list of dims to add new dims in the same order as the other
    types, made all add routines able to optionally return a pointer to the
    newly created object.

Removed some dead code (pg_var(), nc4_pg_var1(), nc4_pg_varm(), misc. small
    routines, etc)

Fixed fill value handling for string types in nc4_get_vara().

Changed many malloc()+strcpy() pairs into calls to strdup().

Cleaned up misc. other minor Coverity issues.
Merge branch 'master' of https://github.com/Unidata/netcdf-c
Merge remote-tracking branch 'upstream/master'
Correct order of unlimited dim checking in test.  (Was relying on old behavior
of backwards ordering)
Switch test for nc_inq_unlimdim and nc_inq_unlimdims to use the same ordering as
the rest of the dimension queries.  Correct error in library where types used
in sub-group variables but that were added to the file after the sub-group was
created weren't available for sub-group variables to use.  Start cleaning up
test suite and un-commenting tests that were commented out (got up to
nc_test4/tst_fills2.c, alphabetically) before running into an error in HDF5.
Removed reference to old test file.
Added entry for fix.
Replaced a comparison of floating point variables to a difference/epsiolon test.
Corrected a double-free issue reported by Coverity.
Merge branch 'master' of https://github.com/Unidata/netcdf-c
Rebasing
Updated RELEASE NOTES, bumped revision to rc6 in preparation for forthcoming release candidate.
Updated Release Notes.
Updated links on Windows download document to reflect new file names.
Bumped revision in configure.ac, CMakelists.txt.
fix typo
null fix
[NCF-273]/HZY-708311

Add a new function called nc_inq_format_extended that
returns more detailed format information (vis-a-vis
nc_inq_format) about an open dataset.

Note that the netcdf API will present the file as if it had
the format specified by nc_inq_format.  The true file
format, however, may not even be a netcdf file; it might be
DAP, HDF4, or PNETCDF, for example. This function returns
that true file type.  It also returns the effective mode for
the file.

signature: nc_inq_format_extended(int ncid, int* formatp, int* modep)
where
* ncid is the NetCDF ID from a previous call to nc_open() or
  nc_create().
* formatp is a pointer to a location for returned true format.
* modep is a pointer to a location for returned mode flags.

Refer to the actual list in the file netcdf.h to see the
currently defined set.

Also added test cases (tst_formatx*).
Corrected a typo re: current version.
Corrected "BAIL" macros to avoid infinite loop when logging is disabled and an
    error occurs after an "exit:" label.

Corrected a dozen Coverity errors (mainly allocation issues, along with a few
    other things):
        711711, 711802, 711803, 711905, 970825, 996123, 996124, 1025787,
        1047274, 1130013, 1130014, 1139538

Refactored internal fill-value code to correctly handle string types, and
    especially to allow NULL pointers and null strings (ie. "") to be
    distinguished.  The code now avoids partially aliasing the two together
    (which only happened on the 'write' side of things and wasn't reflected on
    the 'read' side, adding to the previous confusion).

    Probably still weak on handling fill-values of variable-length and compound
    datatypes.

Refactored the recursive metadata reads a bit more, to process HDF5 named
    datatypes and datasets immediately, avoiding chewing up memory for those
    types of objects, etc.

Finished uncommenting and updating the nc_test4/tst_fills2.c code (as I'm
    proceeding alphabetically through the nc_test4 code files).