Fix for MSVC

[victor-zou]

Three places need to fix if want to compile with MSVC:

1. complex types in MSVC-C is _Fcomplex and _Dcomplex, not conforming to C99 , should should replace xxx _Complex with following macro:

#ifndef HPTT_C_FLT_COMPLEX
#ifdef _MSC_VER
  #define HPTT_C_FLT_COMPLEX _Fcomplex
  #define HPTT_C_DBL_COMPLEX _Dcomplex
#else
  #define HPTT_C_FLT_COMPLEX float _Complex
  #define HPTT_C_DBL_COMPLEX double _Complex
#endif
#endif

2. the INLINE macro should add specification with MSVC: __forceinline

#if defined(__ICC) || defined(__INTEL_COMPILER) || defined(_MSC_VER)
# define INLINE __forceinline
#elif .....

3. MSVC does not support VLA, should use _alloca instead.

#ifdef _MSC_VER
#define HPTT_DECL_VLA(type_, name_, len_) type_* name_ = reinterpret_cast<type_*>(_alloca(sizeof(type_)*len_));
#else 
#define HPTT_DECL_VLA(type_, name_, len_) type_ name_[len_];
#endif