Avoid function prototype incompatibilities.

Add various function attributes to the exported functions to give the
compiler more information to work with during optimization, and also
specify throw() when compiling with C++ on Linux, in order to adequately
match what __THROW does in glibc.

This resolves #237.

configure.ac

@@ -301,6 +301,7 @@ case "${host}" in
 	AC_DEFINE([JEMALLOC_HAS_ALLOCA_H])
 	AC_DEFINE([JEMALLOC_PURGE_MADVISE_DONTNEED], [ ])
 	AC_DEFINE([JEMALLOC_THREADED_INIT], [ ])
+	AC_DEFINE([JEMALLOC_USE_CXX_THROW], [ ])
 	default_munmap="0"
 	;;
   *-*-netbsd*)