I used to have Mozilla installed, but recently it was upgraded to IceApe v1.07 (aka SeaMonkey -- renamed). I got them through apt-get. How come I can't compile mplayerplugin anymore.

$ ./configure
checking for g++... g++
checking for C++ compiler default output file name... a.out
checking whether the C++ compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables... 
checking for suffix of object files... o
checking whether we are using the GNU C++ compiler... yes
checking whether g++ accepts -g... yes
checking for gcc... gcc
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ANSI C... none needed
checking for a BSD-compatible install... /usr/bin/install -c
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking for pkg-config... /usr/bin/pkg-config
checking pkg-config is at least version 0.9.0... yes
configure: Determining mozilla/firefox packages to build against
checking for MOZPLUG... no
configure: WARNING: mozilla-plugin not found
checking for MOZPLUG... no
configure: WARNING: firefox-plugin not found
checking for MOZPLUG... no
configure: WARNING: seamonkey-plugin not found
checking for MOZPLUG... no
configure: WARNING: xulrunner-plugin not found
configure: error: Unable to find mozilla or firefox development files