speed up compileShader
speed up compileShader

std::regex_search() is a very slow way to search for a fixed string
in a shader program. For a 1 megabyte shader, I was waiting for over
a minute for the regex_search to complete. Now using std::strstr().

patriciogonzalezvivo/glslViewer,jjhoughton/glslViewer,patriciogonzalezvivo/glslViewer,jjhoughton/glslViewer,jjhoughton/glslViewer