test: port libvterm unit test to neovim test suite

These were imported from the v0.3.3 git tag
https://github.com/neovim/libvterm/tree/v0.3.3 and not the latest
commit. This is for compatibility reasons as the libvterm code was
imported from v0.3.3.

test/cmakeconfig/paths.lua.in

@@ -5,6 +5,7 @@ for p in ("${TEST_INCLUDE_DIRS}" .. ";"):gmatch("[^;]+") do
   table.insert(M.include_paths, p)
 end
 
+M.vterm_test_file = "${VTERM_TEST_FILE}"
 M.test_build_dir = "${CMAKE_BINARY_DIR}"
 M.test_source_path = "${CMAKE_SOURCE_DIR}"
 M.test_lua_prg = "${LUA_PRG}"

test/unit/testutil.lua

@@ -151,6 +151,13 @@ local function filter_complex_blocks(body)
         or string.find(line, 'mach_vm_range_recipe')
       )
     then
+      -- HACK: remove bitfields from specific structs as luajit can't seem to handle them.
+      if line:find('struct VTermState') then
+        line = string.gsub(line, 'state : 8;', 'state;')
+      end
+      if line:find('VTermStringFragment') then
+        line = string.gsub(line, 'size_t.*len : 30;', 'size_t len;')
+      end
       result[#result + 1] = line
     end
   end