Avoid shadowing existing declarations (improvements to EIP20) (#1437)

* Avoid shadowing existing declarations
About optional methods, Solidity compiler currently throws this warning: "This declaration shadows an existing declaration.". I suggest to remove names from return parameters of the optional methods to avoid shadowing existing declarations.

* More improvements
- Fixed warning about visibility
- Links to examples are now permanent links
- Added note about Solidity version used in the specifications

EIPS/eip-20.md

@@ -29,7 +29,9 @@ A standard interface allows any tokens on Ethereum to be re-used by other applic
 ## Token
 ### Methods
 
-**NOTE**: Callers MUST handle `false` from `returns (bool success)`.  Callers MUST NOT assume that `false` is never returned!
+**NOTES**:
+ - The following specifications use syntax from Solidity `0.4.17` (or above)
+ - Callers MUST handle `false` from `returns (bool success)`.  Callers MUST NOT assume that `false` is never returned!
 
 
 #### name
@@ -41,7 +43,7 @@ but interfaces and other contracts MUST NOT expect these values to be present.
 
 
 ``` js
-function name() view returns (string name)
+function name() public view returns (string)
 ```
 
 
@@ -53,7 +55,7 @@ OPTIONAL - This method can be used to improve usability,
 but interfaces and other contracts MUST NOT expect these values to be present.
 
 ``` js
-function symbol() view returns (string symbol)
+function symbol() public view returns (string)
 ```
 
 
@@ -66,7 +68,7 @@ OPTIONAL - This method can be used to improve usability,
 but interfaces and other contracts MUST NOT expect these values to be present.
 
 ``` js
-function decimals() view returns (uint8 decimals)
+function decimals() public view returns (uint8)
 ```
 
 
@@ -75,7 +77,7 @@ function decimals() view returns (uint8 decimals)
 Returns the total token supply.
 
 ``` js
-function totalSupply() view returns (uint256 totalSupply)
+function totalSupply() public view returns (uint256)
 ```
 
 
@@ -85,7 +87,7 @@ function totalSupply() view returns (uint256 totalSupply)
 Returns the account balance of another account with address `_owner`.
 
 ``` js
-function balanceOf(address _owner) view returns (uint256 balance)
+function balanceOf(address _owner) public view returns (uint256 balance)
 ```
 
 
@@ -98,7 +100,7 @@ The function SHOULD `throw` if the `_from` account balance does not have enough
 *Note* Transfers of 0 values MUST be treated as normal transfers and fire the `Transfer` event.
 
 ``` js
-function transfer(address _to, uint256 _value) returns (bool success)
+function transfer(address _to, uint256 _value) public returns (bool success)
 ```
 
 
@@ -114,7 +116,7 @@ The function SHOULD `throw` unless the `_from` account has deliberately authoriz
 *Note* Transfers of 0 values MUST be treated as normal transfers and fire the `Transfer` event.
 
 ``` js
-function transferFrom(address _from, address _to, uint256 _value) returns (bool success)
+function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)
 ```
 
 
@@ -128,7 +130,7 @@ clients SHOULD make sure to create user interfaces in such a way that they set t
 THOUGH The contract itself shouldn't enforce it, to allow backwards compatibility with contracts deployed before
 
 ``` js
-function approve(address _spender, uint256 _value) returns (bool success)
+function approve(address _spender, uint256 _value) public returns (bool success)
 ```
 
 
@@ -137,7 +139,7 @@ function approve(address _spender, uint256 _value) returns (bool success)
 Returns the amount which `_spender` is still allowed to withdraw from `_owner`.
 
 ``` js
-function allowance(address _owner, address _spender) view returns (uint256 remaining)
+function allowance(address _owner, address _spender) public view returns (uint256 remaining)
 ```
 
 
@@ -177,7 +179,6 @@ Different implementations have been written by various teams that have different
 - [ConsenSys implementation](https://github.com/ConsenSys/Tokens/blob/fdf687c69d998266a95f15216b1955a4965a0a6d/contracts/eip20/EIP20.sol)
 
 
-
 ## History
 
 Historical links related to this standard: