Remove Gay's dtoa from sources.

LICENSE

 This license applies to all parts of V8 that are not externally
 maintained libraries.  The externally maintained libraries used by V8
 are:
 
   - PCRE test suite, located in
     test/mjsunit/third_party/regexp-pcre.js.  This is based on the
     test suite from PCRE-7.3, which is copyrighted by the University
     of Cambridge and Google, Inc.  The copyright notice and license
     are embedded in regexp-pcre.js.
 
   - Layout tests, located in test/mjsunit/third_party.  These are
     based on layout tests from webkit.org which are copyrighted by
     Apple Computer, Inc. and released under a 3-clause BSD license.
 
-  - Dtoa, located under third_party/dtoa.  This code is copyrighted by
-    David M. Gay and released under an MIT license.
-
   - Strongtalk assembler, the basis of the files assembler-arm-inl.h,
     assembler-arm.cc, assembler-arm.h, assembler-ia32-inl.h,
     assembler-ia32.cc, assembler-ia32.h, assembler.cc and assembler.h.
     This code is copyrighted by Sun Microsystems Inc. and released
     under a 3-clause BSD license.
 
   - Valgrind client API header, located at third_party/valgrind/valgrind.h
     This is release under the BSD license.
 
 These libraries have their own licenses; we recommend you read them,
@@ skipping 18 matching lines @@
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 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.