PR c/48956

gcc/c-family/
* c-common.c (int_safely_convertible_to_real_p): Define.
(unsafe_conversion_p): Check conversions involving complex types.
(conversion_warning): Add new warning message for conversions which
discard imaginary component.
* c-common.h: (enum conversion_safety): Add new enumerator for such
conversions.

gcc/testsuite/
* gcc.dg/Wconversion-complex-c99.c: New test.
* gcc.dg/Wconversion-complex-gnu.c: New test.

From-SVN: r223223