setting and using gb_Helper_set_ld_path and gb_Executable_EXT_for_build
is enough to factorize these out of platform/*

a lot of configuration/definition is shared between platforms that build
using gcc.
This start to regroup things that are common into 2 files
com_GCC_defs.mk and com_GCC_class.mk
this can be expanded to be, more generically com_$(COM)_defs/class

The reson for 2 files is that some step need to modfify common definitions
based on the platform and some common definitions need platform defined
value.
with these 2 files we can do a
platform - compiler - platform - compiler - platfrom
sandwich that should cover every scenario.

This one is pretty bad, especially for those who like to select
ranges using keyboard.

The sd library uses SDI headers, but the corresponding targets
were not declared anywhere.

In some cases like an OLE object inside a textbox, the imported document
was empty. This was due to unremoved text context in dmapper.

Removed the unnecessary option "Simple Handles" with all related
functions and icons.

This follows ca402fa0.

The "in shape" term was confusing since it was false for non-text-frame
shapes all the time.