Introduce `get_output_chunk` that will inflate/deflate all the available
input buffer into the output buffer.  `get_output` will call
`get_output_chunk` in a loop, while other consumers can use it to
inflate only a piece of the data.

Instead of paging to zlib in INT_MAX sized chunks, we can give it
as many as UINT_MAX bytes at a time.  zlib doesn't care how big
a buffer we give it, this simply results in fewer calls into zlib.

zlib will return `Z_BUF_ERROR` whenever there is more input to inflate
or deflate than there is output to store the result.  This is normal for
us as we iterate through the input, particularly with very large input
buffers.

Next to including several files, our "common.h" header also declares
various macros which are then used throughout the project. As such, we
have to make sure to always include this file first in all
implementation files. Otherwise, we might encounter problems or even
silent behavioural differences due to macros or defines not being
defined as they should be. So in fact, our header and implementation
files should make sure to always include "common.h" first.

This commit does so by establishing a common include pattern. Header
files inside of "src" will now always include "common.h" as its first
other file, separated by a newline from all the other includes to make
it stand out as special. There are two cases for the implementation
files. If they do have a matching header file, they will always include
this one first, leading to "common.h" being transitively included as
first file. If they do not have a matching header file, they instead
include "common.h" as first file themselves.

This fixes the outlined problems and will become our standard practice
for header and source files inside of the "src/" from now on.

Error messages should be sentence fragments, and therefore:

1. Should not begin with a capital letter,
2. Should not conclude with punctuation, and
3. Should not end a sentence and begin a new one

`giterr_set()` is used when it is required to format a string, and since
we don't really require it for this case, it is better to stick to
`giterr_set_str()`.

This also suppresses a warning(-Wformat-security) raised by the compiler.

Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>

When we are provided some input buffer (with a length) to inflate,
and it contains more data than simply the deflated data, fail.
zlib will helpfully tell us when it is done reading (via Z_STREAM_END),
so if there is data leftover in the input buffer, fail lest we
continually try to inflate it.

Introduce `git_zstream_inflatebuf` for simple uses.

Introduce `git_buf_grow_by` to incrementally increase the size of a
`git_buf`, performing an overflow calculation on the growth.

Introduce some helper macros to test integer overflow from arithmetic
and set error message appropriately.