[result_of] const-qualified function pointer doesn't work

[Shunsuke Sogame <pstade.mb@…>]

boost::result_of can't work with const-qualified function pointer.

typedef int (*pf_t)(int);
typedef boost::result_of<pf_t(int)>::type result1_t; // ok
typedef boost::result_of<pf_t const(int)>::type result2_t; // doesn't compile.

[Douglas Gregor]

(In [48620]) Fix result_of to work with const-qualified function pointers. Fixes #1310

[Daniel James]

(In [60289]) Merge various result_of changes.

• [42234] Reduce header dependencies, from Shunsuke Sogame. Fixes #1535
• [45256] result_of implementation that makes use of C++0x decltype, from Daniel Walker. Fixes #862.
• [48620] Fix result_of to work with const-qualified function pointers. Fixes #1310
• [60052] Remove use of deprecated config macro in result_of.