Node:Standard Symbols, Next:Default Includes, Up:Common Behavior
All the generic macros that AC_DEFINE a symbol as a result of
their test transform their arguments to a standard alphabet.
First, argument is converted to upper case and any asterisks
(*) are each converted to P. Any remaining characters
that are not alphanumeric are converted to underscores.
For instance,
AC_CHECK_TYPES(struct $Expensive*)
will define the symbol HAVE_STRUCT__EXPENSIVEP if the check
succeeds.