* Preprocessor related fix

1). Accoding to ESSL spec : All macro names containing two consecutive underscores ( __ ) are reserved for future use as predefined macro names, so just report a warning instead of error when the shader defines the macro names begining with  '__';

2. According to spec:  If an implementation does not recognize the tokens following #pragma, then it will ignore that pragma, so report a compile-time warning intead of error for the following statement:
#pragma debug(1.23)

3. The 'defined' macro should be allowed to expand and '__LINE__' should be allowed to be replaced with its original line number (otherwise, other expanding macros may change this value).

4. Add a flag 'indentifierSeen' in PPContext to indicate whether the any non-preprocessor tokens is existed before the extension directives, because the built-in symbols and functions are parsed before paring the user shader, so add a 'shaderSource' flag to check this error only for the user shader source;

5. Add missing type int16 and uint16.

* Add test results, remove restriction of #extension.

1. Remove extension restriction in first line , as this is contraversy now.

2. The following shader is compiled failed as glslang consider the keyword 'defined' can not be undefined(in the 9th line: "#define defined BBB")
The shader is as following:
According to ES3.0 spec: It is an error to undefine or to redefine a built-in (pre-defined) macro name.
This rule is aimed to the  __LINE__,  __FILE__, __VERSION__ and  GL_ES,
the keyword "defined" should not be restricted by this rule,
so change the compile error to warning and make the following shader compile successfully.

* 1. Using relaxedError to control error/warning report level. 2. remove #extension restriction. 3. Fix version related issue.

1. Using relaxedError to control error/warning report level. 2. remove #extension restriction. 3. Fix version related issue.

* Add test results

* Turn conditional warnings about pragma to unconditional ones.