firefox_esr: Remove developer files

/usr/lib/firefox-devel-45.2.0 removed. There are Firefox
Development-Tools.I think, we dont need this directory.
This is 1GB. Same like firefox-47.0.1

firefox_esr.be0

@@ -1,6 +1,6 @@
 #!/bin/env beesh
 
-# BEE_VERSION firefox_esr-45.2.0-0
+# BEE_VERSION firefox_esr-45.2.0-1
 
 #export BEE_TMP_TMPDIR=/dev/shm BEE_TMP_BUILDROOT=/dev/shm/bee-root BEE_MAKEFLAGS='-j80'
 
@@ -59,6 +59,10 @@ mee_install_post() {
         done
     fi
 
+    # remove unneeded firefox-devel
+
+    rm -r ${D}${LIBDIR}/firefox-devel-${PKGVERSION}
+
     # install menu-entry
 
     start_cmd mkdir -p ${D}${DATADIR}/applications