Replace a use of strcpy with memcpy, fixing a crash due to inlining.

On Linux, a use of strcpy caused a crash for unknown reasons when
inlined by -O2, but memcpy does not crash in the same place.
swig bindings: Remove extra scope around temporary sigval.

In SWIG 2.x, (and maybe 1.3?) this extra level of scope causes the
sigval to be destroyed even though a pointer to it is retained and
used shortly after, causing a crash.
swig: Change naming of extended struct to comply with how SWIG 2.x handles structs.
Added expression syntax description to documentation.
Use bulleted lists.
Split bundles of reported signals or connections into multiples of 20 messages to prevent bundle from growing too large.
Add instance-related functions to Windows DLL exports.
Add msig_set_instance_management_callback() to DLL export list.
Renamed MAPPER_TIMETAG_NOW to MAPPER_NOW; also redefined it internally as {0L,1L} to avoid accidental usage - this does not imply anything about immediate dispatch however, since there is no concept of TT_IMMEDIATE in libmapper and all bundles will have real timetags.
Merge remote-tracking branch 'steve/master'
Revision of instance release/release_request logic: devices must pass release messages downstream regardless of whether they are the originating device/instance owner. Release request messages will only be used when sending to instance originator.
If input signal is released locally, send release request upstream but do not release instance.
Use strcmp() instead of strstr() when trying to match signal names in monitor - this was preventing monitors from registerings new signals if their name was a substring of an existing signal.
Added benchmark for expression engine.
Fixed bug in signal history reallocation; initialize to zero.
Added db functions for retrieving exact signals from database; restored substring-matching to cmp_match_signal_device_name().
Modified db update functions to return the number of parameters added or modified. Use this information to only call handlers with MDB_MODIFY if params have actually changed.
Restore testmonitor screen clearing.
Added missing db functions to python bindings.
Free memory used by mapper_connection