typo fix

[mortonjt]

This supersedes #995

Submisison Checklist

• Run tests: ./runCmdStanTests.py src/test
• Declare copyright holder and open-source license: see below

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company):

James Morton on behalf of Simons Foundation

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/

[stan-buildbot]

---

Name	Old Result	New Result	Ratio	Performance change( 1 - new / old )
gp_pois_regr/gp_pois_regr.stan	3.49	3.39	1.03	3.04% faster
low_dim_corr_gauss/low_dim_corr_gauss.stan	0.02	0.02	0.93	-7.53% slower
eight_schools/eight_schools.stan	0.11	0.11	1.01	1.28% faster
gp_regr/gp_regr.stan	0.16	0.16	0.96	-3.8% slower
irt_2pl/irt_2pl.stan	5.28	5.34	0.99	-1.12% slower
performance.compilation	91.23	88.61	1.03	2.87% faster
low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan	8.93	8.89	1.0	0.46% faster
pkpd/one_comp_mm_elim_abs.stan	29.81	29.18	1.02	2.11% faster
sir/sir.stan	132.09	130.13	1.02	1.48% faster
gp_regr/gen_gp_data.stan	0.03	0.04	0.98	-1.84% slower
low_dim_gauss_mix/low_dim_gauss_mix.stan	3.24	3.09	1.05	4.53% faster
pkpd/sim_one_comp_mm_elim_abs.stan	0.38	0.38	0.98	-1.82% slower
arK/arK.stan	1.94	1.92	1.01	0.96% faster
arma/arma.stan	0.64	0.64	1.0	0.34% faster
garch/garch.stan	0.53	0.51	1.03	3.0% faster
Mean result: 1.00352207021

---

Jenkins Console Log
Blue Ocean
Commit hash: 4aac038

---

Machine information

ProductName: Mac OS X ProductVersion: 10.11.6 BuildVersion: 15G22010

CPU:
Intel(R) Xeon(R) CPU E5-1680 v2 @ 3.00GHz

G++:
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.6.0
Thread model: posix

Clang:
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.6.0
Thread model: posix

[bbbales2]

You can edit your post and add the copyright holder after:

(this will be you or your assignee, such as a university or company):

I don't know the legal implications of this, but we always do it. Pull looks good otherwise!

(Edit: click the triple dots in the upper right hand corner of the post to edit)

[mortonjt]

Done, lmk if that is ok. I certify that there is no GPLed code in this PR ;)

[bbbales2]

Good!