Implemented system.get_process_id()

[jgmdev]

This function exposes current lite-xl process id which is needed for LSP servers to properly shutdown in case lite-xl crashes as reported here: lite-xl/lite-xl-lsp#20

[Guldoman]

Yeah, this is useful to have.

Also this made me notice that we're mixing #ifs and #ifdefs. Shouldn't we just use #if everywhere? Or is there any reason for the #ifdefs?

[jgmdev]

Yeah, this is useful to have.

Also this made me notice that we're mixing #ifs and #ifdefs. Shouldn't we just use #if everywhere? Or is there any reason for the #ifdefs?

I just followed the same convention used at the top of system.c

[adamharrison]

Looks good; we can always clean the whole #if vs #ifdef stuff later.