ENH: improvements in profiling (issue #648)

- include amount of free system memory in profiling, which can give an
  indication of when swapping is about to start

- profilingSummary utility to collect profiling from parallel
  calculations. Collects profiling information from processor
  directories and summarize the time spent and number of calls as (max
  avg min) values.

applications/test/sysInfo/Test-sysInfo.C

@@ -30,6 +30,7 @@ Description
 #include "profilingSysInfo.H"
 #include "IOstreams.H"
 #include "endian.H"
+#include "cpuInfo.H"
 
 using namespace Foam;
 
@@ -38,7 +39,9 @@ using namespace Foam;
 
 int main(int argc, char *argv[])
 {
-    profiling::sysInfo().write(Info);
+    profilingSysInfo().write(Info);
+
+    cpuInfo().write(Info);
 
 #ifdef WM_BIG_ENDIAN
     Info