match the varaibles' type for 64-bit compatibility

Since the variables are snd_pcm_uframes_t and snd_pcm_uframes_t is
unsigned long, using unsigned int causes problem when running on a
64-bit binary.

Also fix the branch name of googletest.
diff --git a/WORKSPACE b/WORKSPACE
index 02b57bf..133cfc5 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,5 +3,5 @@
 git_repository(
     name = "googletest",
     remote = "https://github.com/google/googletest",
-    branch = "master",
+    branch = "main",
 )
diff --git a/include/tinyalsa/pcm.h b/include/tinyalsa/pcm.h
index 5c11e2a..9fca92d 100644
--- a/include/tinyalsa/pcm.h
+++ b/include/tinyalsa/pcm.h
@@ -217,16 +217,16 @@
      * silence_size      : 0
      */
     /** The minimum number of frames required to start the PCM */
-    unsigned int start_threshold;
+    unsigned long start_threshold;
     /** The minimum number of frames required to stop the PCM */
-    unsigned int stop_threshold;
+    unsigned long stop_threshold;
     /** The minimum number of frames to silence the PCM */
-    unsigned int silence_threshold;
+    unsigned long silence_threshold;
     /** The number of frames to overwrite the playback buffer when the playback underrun is greater
      * than the silence threshold */
-    unsigned int silence_size;
+    unsigned long silence_size;
 
-    unsigned int avail_min;
+    unsigned long avail_min;
 };
 
 /** Enumeration of a PCM's hardware parameters.