Change "uint" to "unsigned"

This fixes a defect introduced in 25162c79. The "uint" type has not
been explicitly defined here on mingw, causing compilation to fail.

On linux we have this in /usr/include/sys/types.h

/* Old compatibility names for C types.  */
typedef unsigned long int ulong;
typedef unsigned short int ushort;
typedef unsigned int uint;

So it's easy to see how such bugs can creep in.

	* rust-demangle.c (struct rust_demangler): Change type of
	"recursion" to unsigned.
	(RUST_NO_RECURSION_LIMIT): Similarly in cast.