Add interface files to qt lib

QtXi/libQtXi/assert.ixi

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+// Halts the program if the condition is false.  Otherwise, does nothing.
+assert(condition:bool)

QtXi/libQtXi/conv.ixi

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+// String conversion functions
+
+// If "str" contains a sequence of ASCII characters that correctly represent
+// an integer constant n, return (n, true). Otherwise return (0, false).
+parseInt(str: int[]): int, bool
+
+// Return a sequence of ASCII characters representing the
+// integer n.
+unparseInt(n: int): int[]

QtXi/libQtXi/io.ixi

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+// I/O support
+
+print(str: int[])     // Print a string to standard output.
+println(str: int[])   // Print a string to standard output, followed by a newline.
+readln() : int[]      // Read from standard input until a newline.
+getchar() : int       // Read a single character from standard input.
+                      // Returns -1 if the end of input has been reached.
+eof() : bool          // Test for end of file on standard input.

QtXi/libQtXi/timer.ixi

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+// Returns an opaque representation of current time.
+// Note: the contents of the returned array are implementation specific
+// and should not be accessed directly.
+getTimestamp(): int[]
+
+// Returns the time elapsed from r to l (e.g. l - r) in milliseconds,
+// when given two arrays returned by getTimestamp().
+// The behavior when the arrays are not from that function is undefined.
+// The useful range is about 24 days.
+timestampDifference(l:int[], r:int[]): int