d.7: Correct a few typos in the manual page

- s/occurance/occurrence/
- s/Univeristy/University/

MFC after:	5 days

share/man/man7/d.7

@@ -239,7 +239,7 @@ Suitable for timestamping logs.
 .It Ft string Fn strchr "string s" "char c"
 Return a substring of
 .Fa s
-starting at the first occurance of
+starting at the first occurrence of
 .Fa c
 in
 .Fa s .
@@ -277,7 +277,7 @@ returns
 .It Ft string Fn strrchr "string s" "char c"
 Return a substring of
 .Fa s
-starting at the last occurance of
+starting at the last occurrence of
 .Fa c
 in
 .Fa s .
@@ -428,7 +428,7 @@ base.
 .%A Robert N. M. Watson
 .%C Cambridge, United Kingdom
 .%D August 2018
-.%T Univeristy of Cambridge Computer Laboratory
+.%T University of Cambridge Computer Laboratory
 .%R OpenDTrace Specification version 1.0
 .%U https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-924.pdf
 .Re