rewrite comments into one, unified style

code/user/tests/async_cancel/async_cancel.c

@@ -1,3 +1,5 @@
+// User-mode regression test for async_cancel.
+
 #include <stdint.h>
 #include <stddef.h>
 #include <stdlib.h>
@@ -6,16 +8,19 @@
 
 #define EVENT_AUTO_RESET 0u
 
+// Prints the requested operation.
 static void print(const char* s) {
     SYS_WRITE_CONSOLE_REQUEST req = { SysSvFromCstr(s) };
     SysWriteConsole(&req);
 }
 
+// Opens file.
 static uint32_t open_file(const char* path, uint32_t* handleOut) {
     SYS_PATH_HANDLE_REQUEST req = { SysSvFromCstr(path), handleOut };
     return SysOpenFile(&req);
 }
 
+// Prints u64.
 static void print_u64(uint64_t v) {
     char buf[32];
     int i = 0;
@@ -33,6 +38,7 @@ static void print_u64(uint64_t v) {
     }
 }
 
+// Runs the requested operation.
 int main(void) {
     print("async_cancel: start\n");