[dist] update .gitignore

Ignore gcov files.
update debug log

An offset address is not shown properly, when the current instruction is
OP_FINISH.
Fix build on mingw
Add Makefile for mingw
Check __MINGW32__ instead of !defined(_MSC_VER)
[bug] fix deadlock when pthread is used

When onig_free_shared_cclass_table() is called from onig_end(),
THREAD_ATOMIC_START is already called. Thus it may cause deadlock.
[new] add default multithread support

To enable this, enable the following two lines in the regint.h:
/* #define USE_MULTI_THREAD_SYSTEM */
/* #define USE_DEFAULT_MULTI_THREAD_SYSTEM */

Win32 thread is used on Windows.
pthread is used on Unix-like systems.
[dist] add --enable-multithread option in configure
[dist] update configure and config.h.in
[dist] update FAQ about multithreading
[dist] also check pthread library
[dist] update configure and config.h.in
[bug] deadlock occurs when recursive lock is not allowed
[dist] remove a workaround for EditorConfig on Win32

See: https://github.com/editorconfig/editorconfig/issues/125
fix memory leaks

Also add NULL checks for safety.
additional fix for #24

Use xalloca() to allocate a stack.
Merge branch 'topic/multithread'
Merge pull request #33 from mattn/mingw

Fix build on mingw
add a test (Close #24)

Issue #24 has been fixed by the following commits:
 * b9fba1dc63ccb42a86e934011b468e6022fabb74
 * c1fc76b9bd463948ffc5058bc352bf93732f0314
 * a0efc0a200f7108ca3d5ac3039c8f952e0051619

Segmentation fault might occur before the fix.
Merge branch 'master' into tmp/ruby-2.0.x

Conflicts:
	regint.h