optimize #include files with macro guards

[mycoboco]

[mycoboco]

a35a585 has a bug - it cannot properly handle if a pp-directive follows a macro guard, e.g.,

#ifndef FOO
#define FOO
BODY1
#endif

#ifndef BAR
#define BAR
BODY2
#endif

sc incorrectly thinks this optimizable when BAR #defined, thus #undefining FOO does not bring the BODY1 part.

Similar examples include:

#ifndef FOO                                                                                           
#define FOO                                                                                           
BODY                                                                                                  
#endif                                                                                                

#pragma nothing 

and

#pragma nothing                                                                                       

#ifndef FOO                                                                                           
#define FOO                                                                                           
#endif

sc optimizes both even if it should not.

[mycoboco]

Those bugs described above have been fixed by 2187744.

[mycoboco]

Performance improvement by macro guard optimization:

time for i in {1..100}; do sc decl.c > /dev/null 2>&1; done

gcc	without opt	with opt
6.3s	12.0s	9.3s

[mycoboco]

State transition of mg_state and state for macro guard: