Make quickjs version available for C code.

[xeioex]

Currently version is only available as the VERSION file, but some distributions do not provide it as a part of libquickjs packet.

Here are some examples how other projects make their versions available:

#include <libxml/xmlversion.h>
LIBXML_DOTTED_VERSION

#include <zlib.h>
zlibVersion()

#include <openssl/ssl.h>
OPENSSL_VERSION_TEXT

[chqrlie]

Will probably apply @saghul's patch to add JS_GetVersion()