* Merge io.InStream and io.OutStream into io.File
* Introduce io.OutStream and io.InStream interfaces
- io.File implements both of these
* Move mem.IncrementingAllocator to heap.IncrementingAllocator
Instead of:
```
%return std.io.stderr.printf("hello\n");
```
now do:
```
std.debug.warn("hello\n");
```
To print to stdout, see `io.getStdOut()`.
* Rename std.ArrayList.resizeDown to std.ArrayList.shrink.
Old:
```
while (condition; expression) {}
```
New:
```
while (condition) : (expression) {}
```
This is in preparation to allow nullable and
error union types as the condition. See #357
* Fix assertion failure when switching on type.
Closes#310
* Update zig build system to support user defined options.
See #204
* fmt.format supports {sNNN} to set padding for a buffer arg.
* add std.fmt.bufPrint and std.fmt.allocPrint
* std.hash_map.HashMap.put returns the previous value
* add std.mem.startsWith
* `zig build --export [obj|lib|exe]` changed to `zig build_obj`,
`zig build_lib` and `zig build_exe` respectively.
* `--name` parameter is optional when it can be inferred from the
root source filename. closes#207
* `zig build` now looks for `build.zig` which interacts with
`std.build.Builder` to describe the targets, and then the zig
build system prints TODO: build these targets. See #204
* add `@bitcast` which is mainly used for pointer reinterpret
casting and make explicit casting not do pointer reinterpretation.
Closes#290
* fix debug info for byval parameters
* sort command line help options
* `std.debug.panic` supports format string printing
* add `std.mem.IncrementingAllocator`
* fix const ptr to a variable with data changing at runtime.
closes#289
Andrew Kelley