bug#3707: add a configure option to enable profiling

[Dan Nicolaescu]

Building emacs with profiling support is not very straight forward at
the moment.
It would be better if we had a configure option to do it:

./configure --enable-profiling
make

Adding the configure flag can be done like this:

--- configure.in.~1.600.~       2009-06-26 18:46:22.000000000 -0700
+++ configure.in                2009-06-28 06:00:37.000000000 -0700
@@ -273,6 +273,18 @@ if test x$ac_gc_check_cons_list != x ; t
 [Define this to check for errors in cons list.])
 fi
 
+AC_ARG_ENABLE(profiling,
+[  --enable-profiling
+                 Build emacs with profiling support],
+[ac_enable_profiling="${enableval}"],[])
+if test x$ac_enable_profiling != x ; then
+   PROFILING_CFLAGS="-DPROFLING -pg"
+   PROFILING_LDFLAGS="-pg"
+else
+   PROFILING_CFLAGS=
+   PROFILING_LDFLAGS=
+fi
+
 #### Make srcdir absolute, if it isn't already.  It's important to
 #### avoid running the path through pwd unnecessarily, since pwd can
 #### give you automounter prefixes, which can go away.  We do all this


How can PROFILING_CFLAGS and PROFILING_LDFLAGS be added to the default
CFLAGS in the Makefile to enable "make" to just DTRT?