cmake: add -Wl,--as-needed linker flag
npwrapper: add missing dependencies, also reorder a bit
cmake: remove -lpthread from linker_flags

also link against CMAKE_THREAD_LIBS_INIT where missing

cmake: link crashuploader against thread libs

cmake: add some more linker libs

cmake: link webcore against thread lib
cmake: OpenSSL is only required if we build curl
npwrapper: add --no-as-needed and link against GTK
ebuild: we don't to filter out --as-needed anymore
Merge pull request #463 from karolherbst/gentoo_bugs

Gentoo bug fixes