i#7046 Add Linux support to dr_create_memory_dump.

[ivankyluk]

This is the first change to add Linux support to dr_create_memory_dump. The memory dump is written in ELF format and save under the logs directory following the WIN example.

The code is test with the following change:

•    dr_memory_dump_spec_t spec;
  

•    spec.size = sizeof(dr_memory_dump_spec_t);
  

•    spec.flags = DR_MEMORY_DUMP_ELF;
  

•    dr_create_memory_dump(&spec);
  

and use "readelf -a" to ensure the elf file is built correctly.

Issue: #7046