Tidy up 32 and 64 bit build support (fix #49):

This fixes up support for building both 32 and 64 bit targets, especially on Windows.

Jamroot

@@ -100,6 +100,7 @@ project beast
     <toolset>clang:<cxxflags>-std=c++11
     <toolset>msvc:<define>_SCL_SECURE_NO_WARNINGS=1
     <toolset>msvc:<define>_CRT_SECURE_NO_WARNINGS=1
+    <toolset>msvc:<cxxflags>-bigobj
     <os>LINUX:<define>_XOPEN_SOURCE=600
     <os>LINUX:<define>_GNU_SOURCE=1
     <os>SOLARIS:<define>_XOPEN_SOURCE=500