Macros: dot_a_linkage and static Macros

Use dot_a_linkage for the Keyboardio-Macros library, and as a
consequence, declare the Macros variable static instead of extern, so
that it gets compiled and linked in even when not referenced directly.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

libraries/Keyboardio-Macros/library.properties

@@ -7,3 +7,4 @@ paragraph=...
 category=Communication
 url=https://github.com/keyboardio/KeyboardioFirmware
 architectures=avr
+dot_a_linkage=true

libraries/Keyboardio-Macros/src/Keyboardio-Macros.cpp

@@ -57,5 +57,3 @@ static bool handleMacroEvent(Key mappedKey, byte row, byte col, uint8_t keyState
 Macros_::Macros_ (void) {
     event_handler_hook_add (handleMacroEvent);
 }
-
-Macros_ Macros;

libraries/Keyboardio-Macros/src/Keyboardio-Macros.h

@@ -14,4 +14,4 @@ class Macros_ {
     void play(const macro_t *macro_p);
 };
 
-extern Macros_ Macros;
+static Macros_ Macros;