Add file comments

base64.c

@@ -29,6 +29,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+/*
+ * Base64 encoding functions.
+ */
+
 /*
  * Base64 decode insz bytes from in.
  * Returns allocated buffer containing outsz bytes.

url.c

@@ -29,6 +29,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+/*
+ * URL encoding functions.
+ */
+
 /*
  * URL decode insz bytes from in.
  * Returns allocated buffer containing outsz bytes plus a '\0' terminator.

util.c

@@ -28,6 +28,10 @@
 
 #include <string.h>
 
+/*
+ * Various utility functions.
+ */
+
 /*
  * Returns a pointer to the first non-whitespace character in s.
  */