NOTE: this is just a sample of how building Symbian specific
extensions COULD work.  This is most probably far from the best
or final way of doing things.

The Moped::Msg currently defines just a single static method,
get_gsm_network_info(), which returns the GSM network and cell id.

The extension code is in Msg.xs (which gets translated by xsubpp into
Msg.cpp), the Perl glue code is in Msg.pm.  To understand the .xs
syntax studying perlxstut and perlxs is recommended.

The prerequisites for compiling this extension are:

(1) The Perl for Symbian SDK installed (either done "make sdkinstall",
    or separately installed the perlXYZsdk.zip).

(2) The etelbgsm.h header, which is available for example from
    the Symbian 6.1 SDK (the Communicator SDK). This must be
    copied to ...\epoc32\include.

(3) The etel.lib and the gsmbas.lib, they should come both
    with the 6.1 and 7.0s SDK.  The WINS udeb and THUMB urel
    versions of these must be copied to the directories
    ...\epoc32\release\wins\udeb and ...\epoc32\release\thumb\urel,
    respectively.

To compile (assuming Perl 5.9.3 and Series 60 SDK 2.6 for Visual C):

  perl \symbian\perl\5.9.3\bin\xsbuild.pl --cpp --extversion=0.1 ext\symbian\Moped\Msg

The --symbian indicates the Symbian and SDK version, the --cplusplus
indicates that one should generate a .cpp file instead of a .c file.

The xsbuild.pl both configures and builds the extension.
To clean do "make clean" or "make distclean".

The location.pl demonstrates using the extension.

To create a SIS:

  makesis -d%EPOCROOT% ext\Moped\Msg\Msg.pkg

TODO: automate the determination of the EXTVERSION (from .pkg?)
and of creation of .pkg (the location of the .dll in the build
and in the target).