* acgeneral.m4 (_AC_TRY_CPP): New macro. It runs the preprocessor

* acgeneral.m4 (_AC_TRY_CPP): New macro. It runs the preprocessor
and checks whether it produces errors or warnings. Don't put grep
output into a variable, use another grep instead.
(AC_TRY_CPP): Use _AC_TRY_CPP. Copy conftest.err to config.log
if the case of an error.
* aclang.m4 (AC_LANG(C), AC_LANG(C++), AC_LANG(Fortran 77)):
define AC_LANG_ABBREV to the short language name.
(_AC_PROG_CPP_WORKS): New macro. It checks whether the current
preprocessor can be used to check for existance of headers.
Most code taken from ...
(AC_PROG_CPP): ... here. Use _AC_PROG_CPP_WORKS. Use shell
"for" to find working CPP. Use AC_LANG_PUSH(C) and AC_LANG_POP -
it's a macro for C only.
(AC_PROG_CXXCPP): Rewritten using _AC_PROG_CPP_WORKS.