Added support for bundled flatfile, cdb and cdb_make handlers
to win32 build of the dba extension.

-Centralise open stream for builtin modules that use streams
-If locks work on database file then only one stream open call is used

-lock support moved from dba_flatfile.c to dba.c
-flatfile, cdb, cdb_make use locking now
#locking is blocking per default use 'rt', 'wt', ct' or 'nt' for non blocking alias
#test access

-lock support moved from dba_flatfile.c to dba.c
-flatfile, cdb, cdb_make use locking now
#locking is blocking per default use 'rt', 'wt', ct' or 'nt' for non blocking alias
#test access to a database file.
#locking uses flock() which will be emulated or warned if that is not eally
#possible in ext/standard/flock_compat.c

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not needed anywhere here

-rename anything to flatfile_xxx/FLATFILE_xxx
-fix update function
-add warnings for update function

emalloc never returns 0, so we can simplify the code paths.
also replace ecalloc with emalloc+memset, so that the latter can be inlined.

fix locks and reading
#i will extend the tests to guard on such failures

Use the the name 'flatfile' correctly so the handler support can be built now.
#I do not like the lock solution since a crashed php would leave the *lck
#file locked now.