Makefile.sub: C99 mathematics functions

* win32/Makefile.sub (config.h): fix version number of runtime
  library.  log2 needs to be defined, not only HAVE_LOG2.
  [ruby-core:57992] [Bug #9044]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43407 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

win32/Makefile.sub

@@ -636,12 +636,13 @@ $(CONFIG_H): $(MKFILES) $(srcdir)/win32/Makefile.sub $(win_srcdir)/Makefile.sub
 #define GETGROUPS_T int
 #define RETSIGTYPE void
 #define TYPEOF_TIMEVAL_TV_SEC long
-!if $(RT_VER) >= 1200
+!if $(RT_VER) >= 120
 #define HAVE_ACOSH 1
 #define HAVE_ASINH 1
 #define HAVE_ATANH 1
 #define HAVE_CBRT 1
 #define HAVE_LOG2 1
+#define log2(x) log2(x)
 #define HAVE_ERF 1
 #define HAVE_ERFC 1
 #define HAVE_ROUND 1