Migrate startdwarf from Ruby to Lua

DFHack/dfhack#2081

startdwarf.lua

@@ -0,0 +1,32 @@
+-- change number of dwarves on initial embark
+
+--[====[
+
+startdwarf
+==========
+Use at the embark screen to embark with the specified number of dwarves.
+
+- ``startdwarf 10`` would just allow a few more warm bodies to dig in
+- ``startdwarf 500`` would lead to a severe food shortage and FPS issues
+
+The number must be 7 or greater.
+
+]====]
+
+local addr = dfhack.internal.getAddress('start_dwarf_count')
+if not addr then
+    qerror('start_dwarf_count address not available - cannot patch')
+end
+
+local num = tonumber(({...})[1])
+if not num then
+    qerror('argument must be a number')
+elseif num < 7 then
+    qerror('argument must be at least 7')
+end
+
+dfhack.with_temp_object(df.new('uint32_t'), function(temp)
+    temp.value = num
+    local temp_size, temp_addr = temp:sizeof()
+    dfhack.internal.patchMemory(addr, temp_addr, temp_size)
+end)