* this directory is generated by gitlab-CI jobs but is supposed to be ignored by reuse

Sergey Kosukhin authored 5 years ago and Moritz Hanke committed 5 years ago

* Custom M4 macro are replaced with those to be used in the new ICON building
  system.
* Removed cfortran.h: the mangling scheme for Fortran symbols is detected at
  the configure-time.
* The precious variables for setting flags resuired to enable external
  packages (e.g. MTIME_C_INCLUDE, MTIME_C_LIB, etc.) are renamed to *_CFLAGS
  and *_CLIBS to better reflect their purpose. If those variables are set as
  command-line arguments of the configure script, the script checks only the
  given values literally, i.e. the script does not try to append and check any
  additional linking or compilation flags.
* The definition of functions declared in yac_lapack_interface.h is moved
  to a separate file yac_lapack_interface.c. And the choice of the interface
  is made with a single preprocessor macro YAC_LAPACK_INTERFACE_ID.
* The default suffix for include files for libxml2 is
  <XML2_ROOT>/include/libxml2 instead of <XML2_ROOT>/include.
* The configure script argument '--without-mpi-pack-external' is renamed to
  '--disable-mpi-pack-external' to reflect that it belongs to the section
  'Optional Features' and not to 'Optional Packages'. If the usage of
  MPI_Pack_external is disabled, the corresponding configure-time tests are
  skipped.
* The configure script argument '--without-regard-for-quality' is renamed to
  '--enable-mpi-checks' (defaults to 'yes'). Previously, the argument allowed
  for ignoring the failures of the configure-time tests of MPI_Pack_external.
  Now the argument allows for skipping the tests at all when specifying a
  valid interactive MPI_LAUNCH command is not possible.
* MPI_LAUNCH does not have to be a full path to an MPI launcher executable
  anymore: the value of the variable is interpreted as a command.
* AR, ARFLAGS, and RANLIB are precious variable now and appear in the help
  message of the configure script.
* The configure script does not try to detect MPI libraries, it only checks
  whether they are available (see comments in configure.ac).

config.h cannot become a part of the public interface (i.e. to be
installed) because it would pollute the namespace of the users's
code, it contains potentially confusing definitions (e.g. type of
the lapack interface used by YAC, which user's code should not
account for), and it contains compiler-specific definition of the
'restrict' keyword. At the same time, it is important to provide
the user's code with some of the details on how YAC is configured
(e.g. whether XML functionality is available, see macro
YAC_XML_ENABLED). Plus header files that become part of the public
interface (e.g. yac_interface.h) provide different interface
depending on the configuration, which means that the required
details must be provided in a public header file. File 'yac_config.h'
is supposed to be that file (see 'yac_config.h.in' for details).
The general recomendations on when each of the files should be
included is the following:
1. Source files (.c) in subdirectory 'src' should include 'config.h'
because it provides full information on the configuration, including
the definition of the 'restrict' keyword, which might be necessary
in the future (if not yet).
2. Header files (.h) in subdirectory 'src' should include
'yac_config.h' because this will make it easier to make them part
of the public interface in the future.
3. If a header file (.h) in subdirectory 'src' cannot be satisfied
with the contents of 'yac_config.h' (e.g. it uses the 'restrict'
keyword in a declaration of an inlined function), it can include
'config.h' but such header file cannot become a part of the public
interface.
4. All files outside the 'src' subdirectory should include 'yac_config.h',
especially files in subdirectory 'examples' because they are supposed
to show how to use the public interface of YAC.

Refactoring for lapack interface detection, added a bundled version of LAPACK (based on Netlib clapack).