test: remove the use of curl in the test suite

There were 2 tests using curl:

`test-http-304.js` is removed because it was initially included to test
that the 304 response does not contain a body, and this is already
covered by `test-http-chunked-304.js`.

`test-http-curl-chunk-problem` has been renamed and refactored so
instead of using curl, it uses 2 child node processes: one for sending
the HTTP request and the other to calculate the sha1sum. Originally,
this test was introduced to fix a bug in `nodejs@0.2.x`, and it was not
fixed until `nodejs@0.2.5`. A modified version of this test has been run
with `nodejs@0.2.0` and reproduces the problem. This same test has been
run with `nodejs@0.2.6` and runs correctly.

Fixes: https://github.com/nodejs/node/issues/5174
PR-URL: https://github.com/nodejs/node/pull/5750


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>