kind=added
names=have_var
visibility=private 

--- have_var(var, headers = nil, &b)
Returns whether or not the variable +var+ can be found in the common
header files, or within any +headers+ that you provide.  If found, a
macro is passed as a preprocessor constant to the compiler using the
variable name, in uppercase, prepended with 'HAVE_'.

For example, if have_var('foo') returned true, then the HAVE_FOO
preprocessor macro would be passed to the compiler.

