Add an example pb_syshdr.h file for platforms without C99.

This allows building the tests easily on Visual C++ in C mode.

Also add checks to pb.h that the defined integer types are of
the proper sizes. This may prevent some difficult to debug problems
later..

tests/SConstruct

@@ -12,6 +12,13 @@ env.Append(PROTOCPATH = ['#../generator', '/usr/include', '.'])
 # Define the include path to find nanopb.proto
 env.Append(PROTOCPATH = ['#../generator', '/usr/include', '.'])
 
+# If the platform doesn't support C99, use our own header file instead.
+conf = Configure(env)
+if not conf.CheckCHeader('stdbool.h'):
+	conf.env.Append(CPPDEFINES = {'PB_SYSTEM_HEADER': '\\"pb_syshdr.h\\"'})
+	conf.env.Append(CPPPATH = "#../compat")
+env = conf.Finish()
+
 # Now include the SConscript files from all subdirectories
 SConscript(Glob('*/SConscript'), exports = 'env')