New test file 'memerr.lua'

Tests for memory-allocation errors moved from 'api.lua' to this new
file, as 'api.lua' was already too big. (Besides, these tests have
nothing to do with the API.)

testes/all.lua

@@ -182,6 +182,7 @@ dofile('nextvar.lua')
 dofile('pm.lua')
 dofile('utf8.lua')
 dofile('api.lua')
+dofile('memerr.lua')
 assert(dofile('events.lua') == 12)
 dofile('vararg.lua')
 dofile('closure.lua')