Move some scripts from root directory to scripts/dev/

At the time of this commit, there is a dedicated folder for development
related tools and such scripts might fit better there to not bloat the
project root directory too much.

Move snapshot to scripts/dev/snapshot

scripts/dev/snapshot

@@ -0,0 +1,7 @@
+#! /bin/sh
+
+if test -n "$1"; then
+  flags="DISTNAME=$1"
+fi
+
+${MAKE:-make} $flags -f build/build.mk snapshot

scripts/dev/vcsclean

@@ -0,0 +1,7 @@
+#! /bin/sh
+
+if test -d '.git' -o -f '.git'; then
+    ${MAKE:-make} -f build/build.mk gitclean-work
+else
+    echo "Can't figure out your VCS, not cleaning."
+fi