Fix inclusions of double-conversion to use proper path

Summary: Will commit in tandem with D1171409.

Test Plan: built folly

Reviewed By: tudorb@fb.com

FB internal diff: D1189713

folly/Conv.h

@@ -39,7 +39,8 @@
 
 #include <limits.h>
 
-#include "double-conversion.h"   // V8 JavaScript implementation
+// V8 JavaScript implementation
+#include <double-conversion/double-conversion.h>
 
 #define FOLLY_RANGE_CHECK(condition, message)                           \
   ((condition) ? (void)0 : throw std::range_error(                      \

folly/Format.h

@@ -26,7 +26,7 @@
 #include <map>
 #include <unordered_map>
 
-#include <double-conversion.h>
+#include <double-conversion/double-conversion.h>
 
 #include "folly/FBVector.h"
 #include "folly/Conv.h"

folly/configure.ac

@@ -54,10 +54,10 @@ AX_BOOST_SYSTEM
 AC_HEADER_STDC
 AC_CHECK_HEADERS([fcntl.h features.h inttypes.h limits.h stdint.h stdlib.h string.h sys/time.h unistd.h mutex.h malloc.h emmintrin.h byteswap.h bits/functexcept.h])
 
-AC_CHECK_HEADER(double-conversion.h, [], [AC_MSG_ERROR(
+AC_CHECK_HEADER(double-conversion/double-conversion.h, [], [AC_MSG_ERROR(
                 [Couldn't find double-conversion.h, please download from \
                 http://code.google.com/p/double-conversion/])], [])
-AC_CHECK_LIB([double_conversion_pic],[ceil],[],[AC_MSG_ERROR(
+AC_CHECK_LIB([double-conversion],[ceil],[],[AC_MSG_ERROR(
              [Please install double-conversion library])])
 
 # Checks for typedefs, structures, and compiler characteristics.