For consistent indentation, change mixed indentation into one.
As the libhangul and previous code base uses 4 spaces for indentation,
convert all tab characters into 4 spaces.

Signed-off-by: JaeSang Yoo <[email protected]>

1. Bracket ('{') rules
   * Functions, structure, union, class, enums
     Opening and closing brackets are placed on separate line.
   * Control-flow statements (ex. if, for, while...)
     Opening bracket should be in same line.
     If-else like code blocks, closing bracket can be in same line.
     (ex. "} else {")
2. Newline ('\n') rules
   * Definition/declaration of functions
     All keywords related with signature should be in same line.
     (extern/static, return type, parameters)
     When the signature is too long to represent in single line,
     try to break in parameters.
   * Space between function & etc.
     Use single newline to split paragraph in function code blocks.
     Use double newline to distinguish between function definitions.
     No need to use additional newline for declaring multiple functions.
3. Spacing rules
   * Control-flow statements
     Split control-flow statements, conditions, bracket with spaces.
   * Definition/declaration of functions
     Do not split function name and its parameter definition.
   * Calling functions
     Do not split argument passing parenthesis of function call.

Signed-off-by: JaeSang Yoo <[email protected]>

* declare conversion functions near its related constants definition
* change magic numbers (conversion result) into constants

Signed-off-by: JaeSang Yoo <[email protected]>

* Prefer use single line comment with //
  * To describe simple comment about codeblock below
  * To describe after the code line
* Prefer use multiple line comment with /* */
  * Always use /* */ for multiple line comment
  * To emphasize code block below
    (ex. Interface Implementation)
  * Documentation such as doxygen (not applied yet)

Signed-off-by: JaeSang Yoo <[email protected]>

* Defines coding convention
* Rules are proposed in commit bb79de2, 9b76bfe, 5c22882
* General rules are refereneced from zeromq

Signed-off-by: JaeSang Yoo <[email protected]>