Remove the version parameter to build_lib()

See mozilla/rust@a6a31ec
Attempt to fix the rustpkg build

These changes are modeled after the fancy-lib test code:
https://github.com/mozilla/rust/tree/master/src/librustpkg/testsuite/pass/src/fancy-lib
Use drop() to fix unused result warnings
Move away from rustpkg
Remove `extern mod rustpkg`
Update for io::io_error being removed

See mozilla/rust#11946
Update for new locations of TreeMap and getopts
Fix the PCRE_LIBDIR envvar used by Travis
Add an example linker error message to the README
Fix issues with ptr::* changes