This change allows you to add a new packet-*.c file and not cause a
recompilation of everything that #include's packet.h
Add the plugin_api.[ch] files ot the plugins/Makefile.am packaging list.
Add #define YY_NO_UNPUT 1 to the lex source so that the yyunput symbol
is not defined, squelching a compiler complaint when compiling the generated
C file.
svn path=/trunk/; revision=1637
Gilbert Ramirez