[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.
Merge branch 'master' of https://github.com/Unidata/netcdf-c
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.