scons: Add an analyze option.

For Clang static code analyzer, the scan-build script will produce more
comprehensive output.  Nevertheless you can invoke it as

  CC=clang CXX=clang++ scons analyze=1

For MSVC this is the best way to use its static code analysis.  Simply
invoke as

  scons analyze=1

Reviewed-by: Brian Paul <brianp@vmware.com>
diff --git a/common.py b/common.py
index 22c1725..d6e6215 100644
--- a/common.py
+++ b/common.py
@@ -91,6 +91,7 @@
 	opts.Add(EnumOption('platform', 'target platform', host_platform,
 											 allowed_values=('cygwin', 'darwin', 'freebsd', 'haiku', 'linux', 'sunos', 'windows')))
 	opts.Add(BoolOption('embedded', 'embedded build', 'no'))
+	opts.Add(BoolOption('analyze', 'enable static code analysis where available', 'no'))
 	opts.Add('toolchain', 'compiler toolchain', default_toolchain)
 	opts.Add(BoolOption('gles', 'EXPERIMENTAL: enable OpenGL ES support', 'no'))
 	opts.Add(BoolOption('llvm', 'use LLVM', default_llvm))