Fold conv package into fmt

Both packages had nearly identical dependency requirements, so merging
them should help reduce the complexity of the build graph.

third_party/dlmalloc/dlmalloc.c

@@ -2,8 +2,8 @@
 #include "libc/bits/safemacros.internal.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/struct/sysinfo.h"
-#include "libc/conv/conv.h"
 #include "libc/dce.h"
+#include "libc/fmt/conv.h"
 #include "libc/limits.h"
 #include "libc/macros.h"
 #include "libc/mem/mem.h"

third_party/dlmalloc/dlmalloc.mk

@@ -27,7 +27,6 @@ THIRD_PARTY_DLMALLOC_A_CHECKS =					\
 THIRD_PARTY_DLMALLOC_A_DIRECTDEPS =				\
 	LIBC_BITS						\
 	LIBC_CALLS						\
-	LIBC_CONV						\
 	LIBC_FMT						\
 	LIBC_NEXGEN32E						\
 	LIBC_RUNTIME						\

third_party/dlmalloc/mtrace.c

@@ -17,7 +17,7 @@
 │ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA                │
 │ 02110-1301 USA                                                               │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/conv/itoa.h"
+#include "libc/fmt/itoa.h"
 #include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
 #include "third_party/dlmalloc/dlmalloc.internal.h"