Add a Boost Jam test for reporting unexpected end of file errors.

[jurko.gospodnetic@…]

We should add a Boost Jam test making sure Boost Jam reports the its unexpected EOF error correctly, including listing the correct EOF information.

We should test the following cases:

1. A Jamfile containing only 'import'. This should report the error on line 1. Ideally, this should report an error about a missing file name but for now an unexpected end of file error is good enough.
2. A Jamfile containing only 'import' and a few more new-lines and white spaces. This should report an error about an unexpected end of file and point to line 1.
3. Same as test case 1, but adding a few more valid code lines before the breaking line.
4. Same as test case 2, but adding a few more valid code lines before the breaking line.
5. Main Jamfile including a file like the one used under test cases 1, 2, 3 & 4.
6. Jamfile containing an unclosed action body spanning multiple lines. Should report an error about the action body not being closed pointing to the start of the action body. Should also report an unexpected EOF error and point to the end of the file.
7. Main Jamfile including a file like the one used in test case 6.

Without this kind of tests touching the Boost Jam error handling code is just too dangerous.