Virtual dynamic shared objects, or vdso files were
not loaded for Linux OS.In Bug 17384 the call
stack could not be unwinded from functions
residing in the vdso object.
This commit adds support for loading such files by
reading the Aux vectors since a vdso is invisibily
mapped to the inferiors address space and the
actual file is not present in the filesystem. The
presence of the vdso is detected by inspecting
the Aux vector for AT_SYSINFO_EHDR tag.