Shell functions pointlessly specialized on _AC_LANG_ABBREV

[Zack Weinberg]

While poking at something else, I happened to notice that we seem to be 
defining redundant copies of many shell functions, one for each language 
under test.  Concretely, if you do this:

    AC_INIT([test], [0.0.0])
    AC_CONFIG_HEADERS([config.h])

    AC_PROG_CC
    AC_PROG_CXX

    AC_LANG([C])
    AC_CHECK_HEADERS([stddef.h])
    AC_LANG([C++])
    AC_CHECK_HEADERS([cstddef])

    AC_OUTPUT

the generated configure script will contain functions named 
'ac_fn_c_check_header_compile' and 'ac_fn_cxx_check_header_compile' (and 
also 'ac_fn_c_try_compile' and 'ac_fn_cxx_try_compile') whose bodies are 
character-for-character identical, and both of which depend on the 
variables set and reset by AC_LANG to control the compiler actually in 
use.  It looks like it has been this way since the shell functions were 
introduced back in 2008.

What was the intention, here? Right now it seems to me that it would 
make most sense to remove _AC_LANG_ABBREV from the function names (so 
there would be just one of each, and it would still depend on the 
current AC_LANG setting).

zw