make realclean should also clean 3rd/libuv and docall
revert +frame-pointer exceptions for gc,callcc

testing showed that forcing %ebp does not help, -O0 for callcc
  and -fno-stack-protector does help, use -O3 fine on gc and internal.
force icc to use stackdir -1, do not test on intel hw.
remove POTION_ARGS_DIR test, not yet needed.
change preferred cc on linux from clang-3.3 to gcc-4.8 (surprise)
add examples target.
pass CC to libuv configure.
do not build extlibs and dynlibs on targets pn, p2.
simplify make test

apparently make test.pn passes all test, but make -j2 test.pn not
disable aio/libuv on cygwin, fix parallel testing problems

cygwin disabled upstream with
https://github.com/joyent/libuv/commit/7f8130a21ba8aaeecc12aa00ebc201e5acf67405

work to revive in https://github.com/rurban/libuv/tree/cygwin
fixup make PLIBS confusion

PNLIB are the potion/p2 shared libs
PLIBS are the names of external libs, which expand to DYNLIBS.
test needs to depend on all libs, othrwise aio and buffile tests fail