Mark several functions static

These are not needed outside of the corresponding compilation units.
Spotted with "-Wmissing-prototypes".

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/config.c

@@ -327,7 +327,7 @@ config_serialize_str (char *dest, const char *val)
  * If ncurses library was compiled with --enable-ext-funcs,
  * then default color is -1.
  */
-void
+static void
 config_color_theme_name (char *theme_name)
 {
 #define MAXCOLORS		8

src/ical.c

@@ -828,7 +828,7 @@ ical_add_exc (llist_t *exc_head, long date)
  * This property defines the list of date/time exceptions for a
  * recurring calendar component.
  */
-void
+static void
 ical_read_exdate (llist_t *exc, FILE *log, char *exstr, unsigned *noskipped,
                   const int itemline)
 {

src/io.c

@@ -324,7 +324,7 @@ io_extract_data (char *dst_data, const char *org, int len)
   *dst_data = '\0';
 }
 
-void
+static void
 display_mark (void)
 {
   const int DISPLAY_TIME = 1;

src/sha1.c

@@ -67,7 +67,7 @@
 #define R4(v, w, x, y, z, i) z += (w ^ x ^ y) + blk (i) + 0xCA62C1D6 + \
     rol (v, 5); w = rol (w, 30);
 
-void
+static void
 sha1_transform (uint32_t state[5], const uint8_t buffer[64])
 {
   typedef union {

src/todo.c

@@ -506,7 +506,7 @@ todo_pipe_item (void)
   wins_unprepare_external ();
 }
 
-void
+static void
 todo_free (struct todo *todo)
 {
   mem_free (todo->mesg);