Move FD_SETSIZE to configure.ac

The commit from the pull request #644 sets the macro FD_SETSIZE to
128 for every host OS, while it is needed on Windows only.
Note that this macro has a much higher value on other OS and after
this commit it get reduced to 128 only.

Since in configure.ac is already present a hook to change the
compile defines for Windows, move there also FD_SETSIZE.

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>

Makefile.am

@@ -37,15 +37,13 @@ DISTCLEANFILES += jimtcl/jsmn/jsmn.o
 endif
 
 # common flags used in openocd build
-AM_CFLAGS = $(GCC_WARNINGS)\
-			  -DFD_SETSIZE=128
+AM_CFLAGS = $(GCC_WARNINGS)
 
 AM_CPPFLAGS = $(HOST_CPPFLAGS)\
 			  -I$(top_srcdir)/src \
 			  -I$(top_builddir)/src \
 			  -DPKGDATADIR=\"$(pkgdatadir)\" \
-			  -DBINDIR=\"$(bindir)\"\
-			  -DFD_SETSIZE=128
+			  -DBINDIR=\"$(bindir)\"
 
 if INTERNAL_JIMTCL
 AM_CPPFLAGS += -I$(top_srcdir)/jimtcl \

configure.ac

@@ -436,7 +436,7 @@ AS_CASE([$host],
     # In case enable_buspirate=auto, make sure it will not be built.
     enable_buspirate=no
 
-    AC_SUBST([HOST_CPPFLAGS], [-D__USE_MINGW_ANSI_STDIO])
+    AC_SUBST([HOST_CPPFLAGS], ["-D__USE_MINGW_ANSI_STDIO -DFD_SETSIZE=128"])
   ],
   [*darwin*], [
     is_darwin=yes