Refactor prof log

Prof logging is conceptually seperate from core profiling, so
split it out as a module of its own.  There are a few internal
functions that had to be exposed but I think it is a fair trade-off.

msvc/projects/vc2017/jemalloc/jemalloc.vcxproj

@@ -58,6 +58,7 @@
     <ClCompile Include="..\..\..\..\src\pages.c" />
     <ClCompile Include="..\..\..\..\src\prng.c" />
     <ClCompile Include="..\..\..\..\src\prof.c" />
+    <ClCompile Include="..\..\..\..\src\prof_log.c" />
     <ClCompile Include="..\..\..\..\src\rtree.c" />
     <ClCompile Include="..\..\..\..\src\sc.c" />
     <ClCompile Include="..\..\..\..\src\stats.c" />

msvc/projects/vc2017/jemalloc/jemalloc.vcxproj.filters

@@ -67,6 +67,9 @@
     <ClCompile Include="..\..\..\..\src\prof.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\..\..\src\prof_log.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
     <ClCompile Include="..\..\..\..\src\rtree.c">
       <Filter>Source Files</Filter>
     </ClCompile>