Refactor Config from a struct to a class.

This should make it easier to add new options, and to add options that
are complex. For example, I want to modify the behavior of
record_allocs_file so that it also enables record_allocs to a default
state.

Test: All unit tests pass.
Test: Enable the backtrace option and restart.
Change-Id: Idf5cdeed06ade3bc2c8ae39d228734bf65209b4f
diff --git a/libc/malloc_debug/RecordData.cpp b/libc/malloc_debug/RecordData.cpp
index c0f3486..5a68deb 100644
--- a/libc/malloc_debug/RecordData.cpp
+++ b/libc/malloc_debug/RecordData.cpp
@@ -185,20 +185,20 @@
   dump_act.sa_sigaction = RecordDump;
   dump_act.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
   sigemptyset(&dump_act.sa_mask);
-  if (sigaction(config.record_allocs_signal, &dump_act, nullptr) != 0) {
+  if (sigaction(config.record_allocs_signal(), &dump_act, nullptr) != 0) {
     error_log("Unable to set up record dump signal function: %s", strerror(errno));
     return false;
   }
   pthread_setspecific(key_, nullptr);
 
   info_log("%s: Run: 'kill -%d %d' to dump the allocation records.", getprogname(),
-           config.record_allocs_signal, getpid());
+           config.record_allocs_signal(), getpid());
 
-  num_entries_ = config.record_allocs_num_entries;
+  num_entries_ = config.record_allocs_num_entries();
   entries_ = new const RecordEntry*[num_entries_];
   cur_index_ = 0;
   dump_ = false;
-  dump_file_ = config.record_allocs_file;
+  dump_file_ = config.record_allocs_file();
 
   return true;
 }