some new autoreconf warnings

[edwardhartnett]

autoreconf -i
aclocal: warning: couldn't open directory 'm4': No such file or directory
libtoolize: putting auxiliary files in '.'.
libtoolize: copying file './ltmain.sh'
libtoolize: putting macros in AC_CONFIG_MACRO_DIRS, 'm4'.
libtoolize: copying file 'm4/libtool.m4'
libtoolize: copying file 'm4/ltoptions.m4'
libtoolize: copying file 'm4/ltsugar.m4'
libtoolize: copying file 'm4/ltversion.m4'
libtoolize: copying file 'm4/lt~obsolete.m4'
configure.ac:1302: warning: The macro `AC_HEADER_STDC' is obsolete.
configure.ac:1302: You should run autoupdate.
./lib/autoconf/headers.m4:704: AC_HEADER_STDC is expanded from...
configure.ac:1302: the top level
configure.ac:1457: warning: The macro `AC_STRUCT_ST_BLKSIZE' is obsolete.
configure.ac:1457: You should run autoupdate.
./lib/autoconf/types.m4:1000: AC_STRUCT_ST_BLKSIZE is expanded from...
configure.ac:1457: the top level
configure.ac:1458: warning: The macro `AC_TRY_RUN' is obsolete.
configure.ac:1458: You should run autoupdate.
./lib/autoconf/general.m4:2997: AC_TRY_RUN is expanded from...
acinclude.m4:9: UD_CHECK_IEEE is expanded from...
configure.ac:1458: the top level
configure.ac:72: installing './compile'
configure.ac:58: installing './config.guess'
configure.ac:58: installing './config.sub'
configure.ac:107: installing './install-sh'
configure.ac:107: installing './missing'
dap4_test/Makefile.am: installing './depcomp'
parallel-tests: installing './test-driver'
ed@mikado:~/netcdf-c$ 

Some of these are new and can be eliminated. I will submit a PR shortly.