Add some paranoia to wtperf's copying and randomizing of values.

refs #1032
Add a Python test that values starting with the LSM tombstone can be inserted and retrieved.

refs #1032
We only append one byte to LSM values that start with the tombstone.

This fixes a bug that caused undefined behavior for applications inserting values into an LSM tree that begin with '\x14\x14'.

refs #1032.
Fix allocation for concatenation of wtperf command-line arguments.

Found when testing #1032 with `valgrind wtperf ... -C buffer_alignment=0`.
Merge branch 'develop' into wtperf-randomize-value
Allow all byte values when wtperf randomizes its values: we will occasionally generate "special" values such as the ones that start with the LSM tombstone.

refs #1032
Fix the pareto calculation in wtperf: __wt_random returns values up to UINT32_MAX, not RAND_MAX.

found when testing for #1032
Factor out the code to generate keys in wtperf, include the trailing NUL in the size.
Minor cleanup of buffer usage, no real change.
Untangle Linux configuration from posix_memalign detection, so we can selectively disable posix_memalign for testing.
Merge pull request #1035 from wiredtiger/wtperf-randomize-value

Add some paranoia to wtperf's copying and randomizing of values.
Merge branch 'develop' into create-config