chore, update sxe-compiler.m4 (use unserding's version)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, import sxe-linker.m4 (for SXE_CHECK_LDFLAGS)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, import sxe-libtool.m4 (for SXE_CHECK_LIBTOOL)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, import tzconv.c and tzconv.m, matlab convenience functions

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, import sxe-matlab.m4 (for SXE_CHECK_MATLAB)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, check for ldflags and libtool

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, check for matlab upon --with-matlab

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, visit contrib/ directory

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, if --with-matlab succeeds, build tzconv.m matlab file

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'contrib/mex-tzconv' into next

* contrib/mex-tzconv:
  minor, if --with-matlab succeeds, build tzconv.m matlab file
  minor, visit contrib/ directory
  chore, check for matlab upon --with-matlab
  chore, check for ldflags and libtool
  chore, import sxe-matlab.m4 (for SXE_CHECK_MATLAB)
  minor, import tzconv.c and tzconv.m, matlab convenience functions
  chore, import sxe-libtool.m4 (for SXE_CHECK_LIBTOOL)
  chore, import sxe-linker.m4 (for SXE_CHECK_LDFLAGS)
  chore, update sxe-compiler.m4 (use unserding's version)