check for invalid code points (jvm port)
Merge pull request #83 from retupmoca/master

Fix release_guide.md step 5
Add --has-libtommath extension.

Enables use of a system libtommath, which is helpful for packagers.
A couple more ChangeLog entries.
Bump VERSION.
Merge pull request #80 from dwarring/master

chr() check for invalid code points (jvm port)
minor optimization
Fix gen2roots compaction optimization bug.

The optimization found the first non-survivor, but then set i = 0 and
so started looking from the start of the list again.
Add flag 'has-sha' to Configure.

Enables use of a system sha-1 library. Also tweaks the 3rdparty code
we ship to have a matching API.
Missing num_roots check in roots optimization.
Compact the gen2 overflows list.

Fixes issue #62.
Minor optimization to MVM_gc_gen2_compact_overflows

ignore moving object until find the first NULL object
Fix decodestream_bytes_to_buf eating too much data

When decodestream_bytes_to_buf needed less data than available in the
buffer, it was incorrectly updating the pointer to the beginning of the
buffer data. This lead to a loss of data when doing small socket reads,
for example.