Examples: convert some files to UTF-8

Those files were in ISO-8859-1 encoding, which is being phased out.

By the way, use typographic quotes.

[skip ci]

examples/NK_baseline.mod

 /*
  * This file implements the Baseline New Keynesian DSGE model described in 
- * much detail in Jesús Fernández-Villaverde and Juan F. Rubio-Ramírez (2006): "A Baseline DSGE 
- * Model", available at http://economics.sas.upenn.edu/~jesusfv/benchmark_DSGE.pdf
+ * much detail in Jesús Fernández-Villaverde and Juan F. Rubio-Ramírez (2006): “A Baseline DSGE 
+ * Model”, available at http://economics.sas.upenn.edu/~jesusfv/benchmark_DSGE.pdf
  *
  * The parametrization is based on the estimated version of this model in 
- * Jesús Fernández-Villaverde (2010): "The econometrics of DSGE models", 
+ * Jesús Fernández-Villaverde (2010): “The econometrics of DSGE models”, 
  * SERIEs, Vol. 1, pp. 3-49, DOI 10.1007/s13209-009-0014-7
  *
  * This implementation was written by Benjamin Born and Johannes Pfeifer. In
@@ -24,7 +24,7 @@
  * example3.mod
  * 
  * The model is written in the beginning of period stock notation. To make the model
- * conform with Dynare's end of period stock notation, we use the 
+ * conform with Dynare’s end of period stock notation, we use the 
  * predetermined_variables-command.
  *
  * Please note that the following copyright notice only applies to this Dynare 

examples/agtrend.mod

 /*
  * This file replicates the model studied in:
- * Aguiar, Mark and Gopinath, Gita (2004): "Emerging Market Business Cycles:
- * The Cycle is the Trend" (NBER WP 10734). It is different from version published 
+ * Aguiar, Mark and Gopinath, Gita (2004): “Emerging Market Business Cycles:
+ * The Cycle is the Trend” (NBER WP 10734). It is different from version published 
  * in the Journal of Political Economy.
  * 
  * This model file is intended to show the capabilities of the Dynare macro 
@@ -15,7 +15,7 @@
  * The mod-file reproduces Figure 4 of the working paper, which displays the
  * model response to 1 percent shock to trend and cyclical TFP.
  *
- * This implementation was written by Sbastien Villemot and Johannes Pfeifer. 
+ * This implementation was written by Sébastien Villemot and Johannes Pfeifer. 
  * Please note that the following copyright notice only applies to this Dynare 
  * implementation of the model.
  */