Port first two patches of branch index-2objc.

We decided to use objects for indexes to ease addition
of more specialized index types (such as primary key tree
indexes, spatial indexes).

Work done by Konstantin Shulgin.

Incorporates review fixes. This patch:

 - makes struct index an Objective C class,
 - adds init and free methods,
 - moves allocation of sp_tree struction to heap (used
 to be allocated in the pool allocator) since we may
 in future create/drop indexes on the fly,
 - updates method calling signatures.

paramaters use floating point representation.

Conflicts:
	test/box/lua.result

Incorporate spelling/grammar mistakes identified during
a review of the user guide, done by courtesy of Peter Gulutzan.

output to user specified buffers

connector/c/tnt: main client library
connector/c/tntsql: sql parser library
connector/c/tntnet: network io library
test/connector_c: test suite for connector/c libraries

lua.result was somehow missed in the last commit, add now

Start extending the manual with Lua stored programs.

An intermediate step, use size0 for 'size' temporarily,
to ensure there are no compilation errors.

This is a code review of Konstantin Shulgin's branch
refactoring-tbuf.

Fix a bug in next slot calculation (creeped in with
code review fixes).