[src/mpfr-impl.h] Removed the detection of possible inconsistencies

under Unix because the tests could yield spurious errors with Cygwin32
or other similar implementations. Moreover, such tests were used for
debugging purpose or to detect potential problems in the environment,
thus were not really useful for the end user. They were initially
added in the win-thread-safe-dll branch (r9682, following a problem
found in r9680). One alternative for checking by the MPFR developers
would be to output the status of some internal macros in tversion.
(merged changeset r10260 from the trunk)

[From SVN r10264 (branches/3.1)]

src/mpfr-impl.h

@@ -252,19 +252,6 @@ typedef struct __gmpfr_cache_s *mpfr_cache_ptr;
 # define MPFR_WIN_THREAD_SAFE_DLL 1
 #endif
 
-/* Detect some possible inconsistencies under Unix. */
-#if defined(__unix__)
-# if defined(_WIN32)
-#  error "Both __unix__ and _WIN32 are defined"
-# endif
-# if __GMP_LIBGMP_DLL
-#  error "__unix__ is defined and __GMP_LIBGMP_DLL is true"
-# endif
-# if defined(MPFR_WIN_THREAD_SAFE_DLL)
-#  error "Both __unix__ and MPFR_WIN_THREAD_SAFE_DLL are defined"
-# endif
-#endif
-
 #if defined(__MPFR_WITHIN_MPFR) || !defined(MPFR_WIN_THREAD_SAFE_DLL)
 extern MPFR_THREAD_ATTR unsigned int __gmpfr_flags;
 extern MPFR_THREAD_ATTR mpfr_exp_t   __gmpfr_emin;