Dump EmittedFunctionDetails to sysimage
Restore linedebug info from sysimage

- Fiddles with FuncInfo struct to optionally store name and filename info
- sysimg_handle -> jl_sysimg_handle (not exported)
- adds jl_restore_linedebug_info(uv_lib_t*)
Merge pull request #6490 from ihnorton/dump_linedebug

Dump EmittedFunctionDetails to sysimage