Workaround for __has_include(<...>) and ICCAVR.

[dhebbeker]

Fixes #592.

[jwellbelove]

I was wondering if the __has_include variation should be qualified with a defined(__AVR__) just in case it breaks an existing user's setup.

[dhebbeker]

As I understand cppreference.com on source file inclusion it should not matter with new whether "" or <> is used.

In order to provide for all contingencies a compiler switch could be introduced. I assume AVR-GCC does behave correctly for __has_include thus it would not need the workaround.

Suggested change

	#define ETL_USING_STD_NEW __has_include("new")
	#if defined(__ICCAVR__)
	#define ETL_USING_STD_NEW __has_include("new")
	#else
	#define ETL_USING_STD_NEW __has_include(<new>)
	#endif

__ICCAVR__ is an integer that is set to 1 when the code is compiled with the IAR C/C++ Compiler for AVR.

[dhebbeker]

In case somebody else stumbles across this issue with ICCAVR. This error occurs in case of an indirection of __has_include(<file>) through a macro. There is no problem with __has_include("file") or without indirection. See example:

test.cpp:

#if __has_include(<cstddef>)
	#warning (1) found header
#else
	#warning (1) did not find header
#endif

#define HAS_INCLUDE1 __has_include("cstddef")
#if HAS_INCLUDE1
	#warning (2) found header
#else
	#warning (2) did not find header
#endif

#define HAS_INCLUDE2 __has_include(<cstddef>)
#if HAS_INCLUDE2 // this is line 15
	#warning (3) found header
#else
	#warning (3) did not find header
#endif

Compile with

iccavr.exe test.cpp --eec++

Output:

   IAR C/C++ Compiler V6.70.1.929 for Atmel AVR
   Copyright 1996-2015 IAR Systems AB.
   Standalone license - IAR Embedded Workbench for Microchip AVR 6.70

        #warning (1) found header
         ^
"test.cpp",2  Warning[Pe1105]:
          #warning directive: (1) found header

        #warning (2) found header
         ^
"test.cpp",9  Warning[Pe1105]:
          #warning directive: (2) found header

  #if HAS_INCLUDE2 // this is line 15
      ^
"test.cpp",15  Error[Pe008]:
          missing closing quote
"test.cpp",15  Internal error:
          [Front end]: assertion failed at:
          "..\..\Translator\compiler_core\src\parser\edg\literals.c", line 1159
Fatal error detected, aborting.

(1) and (2) are OK, whereas (3) produces an internal compiler error.

[jwellbelove]

In that case, there may be a better workaround change.

#if __has_include(<new>)
  #define ETL_USING_STD_NEW 1
#else
  #define ETL_USING_STD_NEW 0
#endif