load librt only once

Drop duplicate calls to `ffi.load(…)` in `ffi/framebuffer_qtfb` and `ffi/input_pocketbook`:
the library is already loaded in the global namespace by `ffi/posix_h`, so `ffi.C` can be
used to access its symbols.

Author: benoit-pierre

ffi/framebuffer_qtfb.lua

@@ -5,13 +5,6 @@ local qtfb = require("ffi/qtfb")
 
 require("ffi/posix_h")
 
--- Fallback/explicit loading of librt for shm_open
-local rt
-local ok = pcall(function() rt = ffi.load("rt") end)
-if not ok or not rt then
-    rt = C
-end
-
 local framebuffer = {
     sock = -1,
     data = nil,
@@ -78,7 +71,7 @@ function framebuffer:init()
 
     -- Open and map shared memory
     local shmName = string.format("/qtfb_%d", shmKey)
-    local shmFD = rt.shm_open(shmName, 2, 0) -- O_RDWR = 2
+    local shmFD = C.shm_open(shmName, 2, 0) -- O_RDWR = 2
     if shmFD < 0 then
         C.close(self.sock)
         self.sock = -1

ffi/input_pocketbook.lua

@@ -1,6 +1,5 @@
 local ffi = require("ffi")
 local C = ffi.C
-local rt = ffi.load("librt.so")
 local inkview = require("ffi/inkview")
 local util = require("ffi/util")
 
@@ -340,7 +339,7 @@ function input:open()
         -- Open the monitor queue. We could technically live without it on older firmwares
         -- that don't have it, but I'm not sure how events are meant to be consumed on there
         -- to prevent stall, so for the time being we bail when we don't see it.
-        local hwinput = rt.mq_open("/hwevent", C.O_RDONLY+C.O_NONBLOCK)
+        local hwinput = C.mq_open("/hwevent", C.O_RDONLY+C.O_NONBLOCK)
         assert(hwinput >= 0, "No /hwevent, probably too old firmware")
         poll_fds[0].fd = hwinput
         poll_fds[0].events = C.POLLIN
@@ -461,7 +460,7 @@ local function waitForEventRaw(timeout)
         -- monitor would spam queued events to whaetever else gets focus after us.
         if band(poll_fds[0].revents, C.POLLIN) ~= 0 then
             updateTimestamp() -- single 'ts' copy for genEmuEvent inside the loop
-            while rt.mq_receive(poll_fds[0].fd, ffi.cast("char*", hwmsg), hwmsg_len, nil) > 0 do
+            while C.mq_receive(poll_fds[0].fd, ffi.cast("char*", hwmsg), hwmsg_len, nil) > 0 do
                 local m = hwmsg[0]
                 -- If there's no raw keymapping, emit this one instead
                 if pb_key_events[m.type] and not raw_keymap then
@@ -518,7 +517,7 @@ end
 function input.closeAll()
     eventq = nil
     if poll_fds ~= nil then
-        rt.mq_close(poll_fds[0].fd)
+        C.mq_close(poll_fds[0].fd)
         for i=1, poll_fds_count-1 do
             C.close(poll_fds[i].fd)
         end