Log Message:
Update to 2.4.2:

Changes from version 2.4.1 to version 2.4.2:
- Security fix in formatted output functions (buffer overflow).
- Formatted output functions: 6 is now the default value for
  empty precision field with %Rf.
- Better portability of configure script.
- Detection of intmax_t and uintmax_t types.
- Improved documentation: mpfr_get_z_exp, mpfr_strtofr, mpfr_get_str and
  formatted output functions.
- Improved message in case of assertion failure.
- Test coverage: 97.0% lines of code.
- Updated tcmp_ld test to really test the long double.
- Some documentation files are installed in $docdir.
- Removed mpfr_init_cache (unused and undocumented function).
- Fixed the way $CC / $CFLAGS are got from gmp.h (__GMP_CC / __GMP_CFLAGS).
- Bug fixes.
- Also note that GCC 4.4.0 (only this obsolete version) does not build
  MPFR 2.4.2 correctly; this is detected by "make check" (failures in
  tget_z and tpow_all).