Start a 'terminal' source subdirectory.

This contains terminal.c, bidi.c (formerly minibidi.c), and
terminal.h. I'm about to make a couple more bidi-related source files,
so it seems worth starting by making a place to put them that won't be
cluttering up the top level.

CMakeLists.txt

@@ -9,6 +9,8 @@ add_subdirectory(doc)
 
 add_compile_definitions(HAVE_CMAKE_H)
 
+include_directories(terminal)
+
 add_library(utils STATIC
   ${GENERATED_COMMIT_C})
 add_dependencies(utils cmake_commit_c)
@@ -41,7 +43,8 @@ add_library(agent STATIC
   sshpubk.c pageant.c aqsync.c)
 
 add_library(guiterminal STATIC
-  terminal.c ldisc.c minibidi.c config.c dialog.c
+  terminal/terminal.c terminal/bidi.c
+  ldisc.c config.c dialog.c
   $<TARGET_OBJECTS:logging>)
 
 add_library(noterminal STATIC

putty.h

@@ -2352,7 +2352,7 @@ void setup_config_box(struct controlbox *b, bool midsession,
                       int protocol, int protcfginfo);
 
 /*
- * Exports from minibidi.c.
+ * Exports from bidi.c.
  */
 #define BIDI_CHAR_INDEX_NONE ((unsigned short)-1)
 typedef struct bidi_char {