All the pre- and post-processing of the startup lib around the main
function of a dynamic program is now done by LDSO. Hence LDSO directly
calls the main function of the program.
Issue #1042
Base libraries are already contained within ldso.lib.so. Remove unnecessary
filtering from 'dep_lib.mk', make ldso depend on base libs.
Issue #1017
Issue #989
For a main thread a thread object is created by the CRT0 before _main gets
called so that _main can already run in a generic environment that, e.g.,
catches stack overflows as a page-fault instead of corrupting the BSS.
Additionally dynamic programs have only one CRT0 - the one of the LDSO -
which does the initialization for both LDSO and program.
ref #989
