ARM: Use libc malloc by default.

I'm not sure how much test Jemalloc gets on ARM, moreover
compiling Redis with Jemalloc support in not very powerful
devices, like most ARMs people will build Redis on, is extremely
slow. It is possible to enable Jemalloc build anyway if needed
by using "make MALLOC=jemalloc".

src/Makefile

@@ -28,11 +28,14 @@ PREFIX?=/usr/local
 INSTALL_BIN=$(PREFIX)/bin
 INSTALL=install
 
-# Default allocator
+# Default allocator defaults to Jemalloc if it's not an ARM
+MALLOC=libc
+ifneq ($(uname_M),armv6l)
+ifneq ($(uname_M),armv7l)
 ifeq ($(uname_S),Linux)
 	MALLOC=jemalloc
-else
-	MALLOC=libc
+endif
+endif
 endif
 
 # Backwards compatibility for selecting an allocator