remove the obsolete 'm4' subdirectory

as far as I can see, it provided M4 macros for autotools based
projects which wanted to use OPM. I have severe doubts that this was
used by anyone because it most likely does not even work. (e.g. the M4
macros does not seem to specify the ERT and opm-parser prerequisites.)

Note that I'm not 100% sure of the above, so if I'm wrong, state so
loudly and I'll close the PR...

cmake/OPM-CMake.md

@@ -226,10 +226,7 @@ Default is OFF.
 
 ### Project-specific Files
 
-All of these files are in the project root, except for `opm-xxx.m4`
+All of these files are in the project root.
-which is in the `m4` directory. (`dunecontrol` always adds this
-subdirectory for all the prerequisites listed in `dune.module`, to the
-search path).
 
 <table><thead><tr><th>File<th>Description<tbody>
 <tr>
@@ -267,18 +264,6 @@ dependencies is taken from opm-xxx-prereqs.cmake and not from here).
 Since this file must be present before the build starts (for dunecontrol),
 the version information is kept here.
 
-<tr>
-<td>	opm_xxx.m4
-<td>
-Tell the generic opm.m4 module which name it should request pkg-config
-for. This module is used by autotools-projects which link to OPM.
-Notice that dashes is replaced by underscore in the filename to be
-compatible with M4. (The actual name of the file doesn't matter to the
-autotools build system). The contents of this file is mostly boiler-plate
-where the names need to be changed to the project in question. (The
-DUNE build system assumes the presence of macros based on the project
-name).
-	
 </table>
 
 ### Project Modules

m4/opm.m4

@@ -1,50 +0,0 @@
-dnl -*- autoconf -*-
-
-dnl OPM_PKG_CONFIG_MODULE (name, version, description)
-dnl
-dnl Common routine to include configuration module for an OPM project
-AC_DEFUN([OPM_CHECK_PKG_MODULE],[
- dnl local variables representing parameters
- m4_pushdef([_opm_name], [$1])
- m4_pushdef([_opm_version], [$2])
- m4_pushdef([_opm_description], [$3])
- 
- dnl macro-friendly version of the name; uppercase and with dashes
- dnl replaced with underscores
- m4_pushdef([_opm_module], [m4_translit(_opm_name,[-],[_])])
- m4_pushdef([_OPM_MODULE], [m4_toupper(_opm_module)])
-
- dnl if we are given the location as a parameter, look there first
- AC_ARG_WITH(_opm_name,
-  AS_HELP_STRING([--with-_opm_name=PATH],[_opm_description directory]))
-
- AS_IF([test -n "$with_[]_opm_module"],[
-  export PKG_CONFIG_PATH=$with_[]_opm_module:$PKG_CONFIG_PATH
- ])
-
- dnl let pkg-config do the heavy lifting of finding the .pc file
- PKG_CHECK_MODULES(_OPM_MODULE,[_opm_name = _opm_version],[
-  AC_DEFINE(HAVE_[]_OPM_MODULE,[1],[_opm_description available])
- ])
-
- dnl TODO: here we could call PKG_CONFIG --variable if we need more
-
- dnl make flag available for Makefiles too
- AM_CONDITIONAL(HAVE_[]_OPM_MODULE, test x$HAVE_[]_OPM_MODULE = x1)
-
- dnl add our libraries to the global list of compiler and linker options
- DUNE_CPPFLAGS="$DUNE_CPPFLAGS $_OPM_MODULE[]_CFLAGS"
- DUNE_LIBS="$DUNE_LIBS $_OPM_MODULE[]_LIBS"
-
- # add this module to summary (if we are used with dunecontrol)
- ifdef([DUNE_MODULE_ADD_SUMMARY_ENTRY],[
-  DUNE_MODULE_ADD_SUMMARY_ENTRY(_opm_name)
- ])
-
- dnl cleanup
- m4_popdef([_OPM_MODULE])
- m4_popdef([_opm_module])
- m4_popdef([_opm_description])
- m4_popdef([_opm_version])
- m4_popdef([_opm_name])
-])

m4/opm_core.m4

@@ -1,12 +0,0 @@
-dnl -*- autoconf -*-
-
-dnl locate opm-core library itself; this macro is called by every module
-dnl that depends on opm-core.
-AC_DEFUN([OPM_CORE_CHECK_MODULE],
-[
- OPM_CHECK_PKG_MODULE([opm-core],[1.0],[OPM Core Library])
-])
-
-dnl find all prerequisites of opm-core; nothing to do here since this
-dnl is done by the CMake module and then stored in the -config file.
-AC_DEFUN([OPM_CORE_CHECKS],[])