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.

tool/decode/lib/asmcodegen.c

@@ -19,7 +19,7 @@
 #include "libc/bits/safemacros.internal.h"
 #include "libc/fmt/fmt.h"
 #include "libc/mem/mem.h"
-#include "libc/runtime/gc.h"
+#include "libc/runtime/gc.internal.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
 #include "tool/decode/lib/asmcodegen.h"

tool/decode/x87.c

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

tool/decode/xor.c

@@ -5,7 +5,7 @@
 │   • http://unlicense.org/                                        │
 │   • http://creativecommons.org/publicdomain/zero/1.0/            │
 ╚─────────────────────────────────────────────────────────────────*/
-#include "libc/runtime/gc.h"
+#include "libc/runtime/gc.internal.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
 #include "libc/x/x.h"

tool/decode/zip.c

@@ -25,7 +25,7 @@
 #include "libc/mem/mem.h"
 #include "libc/nexgen32e/crc32.h"
 #include "libc/nt/struct/filetime.h"
-#include "libc/runtime/gc.h"
+#include "libc/runtime/gc.internal.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/map.h"