bson: improve bson_compare() to look at bson data.

This improves the situation a bit where the first 4 bytes to be looked
at would be the length, and not very useful. We now skip past those
bytes and start at the first field.
build: remove old python prototype.
build: remove Python.m4 from configure.
memory: add bson_mem_set_vtable()

This function allows setting a custom memory allocator. It must be called
at the beginning of the process so that allocations are allocated and freed
by the proper system.
context: use statically allocated default context.

This removes the need for the atexit() handler.
context: remove superfluous malloc
context: protect against destroying the default context.
Fixed typo in json-to-bson documentation.

Some comments in json-to-bson.c were the same as in bson-to-json.c. Some
BSON and JSON's needed to be switched.
Merge pull request #78 from mwhittaker/example-typo

Fixed typo in json-to-bson documentation.
Release 0.98.0!

Signed-off-by: Christian Hergert <christian.hergert@mongodb.com>
build: post-release bump.
doc: fix typos in bson_uint32_to_string docs/comments
Merge pull request #79 from Machyne/master

doc: fix typos in bson_uint32_to_string docs/comments
Fix a bug in json parsing

Fix a bug where we misidentify special mode '$' keys in extended json
parsing.  Basically, we have to verify length for both strings, rather
than relying on prefix matches with strncmp.  We also miscounted length
for the prefix match, allowing any '$' key that started with an '$i' to
match '$id'
Merge pull request #81 from hanumantmk/ISSUE62

Fix a bug in json parsing
doc: fix typo in bson_init_from_json docs
Merge pull request #82 from justincase/patch-1

doc: fix typo in bson_init_from_json docs
Call correct free()
Merge pull request #83 from bjori/patch-2

Call correct free()
doc: fix typo in bson_oid_is_valid comment header