common: Rename binary_find.h to algorithm.h

Makes the header more general for other potential algorithms in the
future. While we're at it, include a missing <functional> include to
satisfy the use of std::less.

src/common/CMakeLists.txt

@@ -95,11 +95,11 @@ add_custom_command(OUTPUT scm_rev.cpp
 )
 
 add_library(common STATIC
+    algorithm.h
     alignment.h
     assert.h
     detached_tasks.cpp
     detached_tasks.h
-    binary_find.h
     bit_field.h
     bit_util.h
     cityhash.cpp

src/common/algorithm.h

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <algorithm>
+#include <functional>
 
 namespace Common {