Ensure that we find required packages

- Add REQUIRES to find_pacakge statements for
  - ZLIB
  - Threads
  - CURL (only when ENABLE_PLUGINS=On)
  - Curses (only when ENABLE_CURSES=On)
  - OpenSSL (only when ENABLE_SSL=On)

- Get rid of conditional checks when using REQUIRED.

- Fix error message if pthreads couldn't be found.
PostgreSQL dissector: Update output format to reflect release syntax for John the Ripper 1.7.9-Jumbo-8. The old format is still supported, but deprecated. Also, change the output for more effective cracking in 'Single' mode.
Merge pull request #132 from justfalter/add_requires

Ensure that we find required packages
Retry read() if it returns EAGAIN or EINTR
Merge pull request #135 from eaescob/master

Change for GTK logo
Merge pull request #134 from kholia/postgres-fixes

PostgreSQL dissector: Update output format.
Merge pull request #138 from eaescob/sslstrip-fixes

Retry read() if it returns EAGAIN or EINTR