glsl/glcpp: Treat CR+LF pair as a single newline

glsl/glcpp: Treat CR+LF pair as a single newline

The GLSL specification says that either carriage-return, line-feed, or both
together can be used to terminate lines. Further, it says that when used
together, the pair of terminators shall be interpreted as a single line.

This final requirement has not been respected by glcpp up until now, (it has
been emitting two newlines for every CR+LF pair).

Here, we fix the lexer by using a regular expression for NEWLINE that eats
up both "\r\n" (or even "\n\r") if possible before also considering a single
'\n' or a single '\r' as a line terminator.

Before this commit, the test results are as follows:

	\r:	135/143 tests pass
	\r\n:	  4/143 tests pass
	\n\r:	  4/143 tests pass

After this commit, the test results are as follows:

	\r:	135/143 tests pass
	\r\n:	140/143 tests pass
	\n\r:	139/143 tests pass

So, obviously, a dramatic improvement.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>