Added definitions for Shift,Ctrl,Alt special keys

Otherwise when definiting glut:special and glut:special-up methods it signals:
Error: 112 is not defined as a value for enum type #<FOREIGN-ENUM CL-GLUT:SPECIAL-KEYS>
Checked on Windows and Linux.

and a cleanup: fixed conditional: #+win32 -> #+windows (ccl does not define win32 on win 64). This has not caused any issue as *gl-get-proc-address* is set elsewhere, but it is the only occurence of win32 conditional in cl-opengl.