Dependencies to be checked by configure are declared within the
<deps> section.
The <deps> tag itself has two attributes: lang
for the programming language you want to have code generated for
and platform for the operating systems to be supported.
Set lang to "c" for plain C code or "c++" for C++ code
generation. By default C code is generated. C++ code generation
should be selected for extensions making use of C++ libraries.
Possible values for platform are unix for all Unix-like platforms
supporting configure scripts, win32 for Microsoft Windows with
Microsoft VisualStudio as developement platform or all for both
supported platforms.
Within the <deps> section it is possible to
define configure parameters, to specify needed header files
and libraries and to add existing files to the extension.