Remove garbage collector macro from header (#114)

We can put this back the moment someone requests it. Pain-free garbage
collection for the C language is pretty cool. All it does is overwrite
the return address with a trampoline that calls free(). It's not clear
what it should be named if it's made a public API.

test/libc/fmt/dirname_test.c

@@ -19,7 +19,7 @@
 #include "libc/fmt/conv.h"
 #include "libc/fmt/fmt.h"
 #include "libc/mem/mem.h"
-#include "libc/runtime/gc.h"
+#include "libc/runtime/gc.internal.h"
 #include "libc/testlib/testlib.h"
 
 TEST(dirname, test) {

test/libc/fmt/fcvt_test.c

@@ -17,7 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/fmt/fmt.h"
-#include "libc/runtime/gc.h"
+#include "libc/runtime/gc.internal.h"
 #include "libc/testlib/testlib.h"
 #include "libc/x/x.h"
 

test/libc/fmt/fmt_test.c

@@ -19,7 +19,7 @@
 #include "libc/fmt/fmt.h"
 #include "libc/limits.h"
 #include "libc/math.h"
-#include "libc/runtime/gc.h"
+#include "libc/runtime/gc.internal.h"
 #include "libc/str/str.h"
 #include "libc/testlib/testlib.h"
 #include "libc/x/x.h"

test/libc/fmt/palandprintf_test.c

@@ -32,7 +32,7 @@
 #include "libc/limits.h"
 #include "libc/math.h"
 #include "libc/mem/mem.h"
-#include "libc/runtime/gc.h"
+#include "libc/runtime/gc.internal.h"
 #include "libc/str/str.h"
 #include "libc/testlib/ezbench.h"
 #include "libc/testlib/testlib.h"

test/libc/fmt/sprintf_s_test.c

@@ -19,7 +19,7 @@
 #include "libc/bits/bits.h"
 #include "libc/bits/safemacros.internal.h"
 #include "libc/fmt/fmt.h"
-#include "libc/runtime/gc.h"
+#include "libc/runtime/gc.internal.h"
 #include "libc/testlib/testlib.h"
 #include "libc/x/x.h"