Use "p" instead of ``p''.

Andrew tells me that's a LaTeX-ism.

src/naming.adoc

@@ -79,7 +79,7 @@ of the P extension.
 Standard unprivileged extensions can also be named by using a single "Z" followed by an
 alphanumeric name. The name must end with an alphabetical character or an 
 optional version number. The second letter from the end cannot be numeric if the
-last letter is ``p''. For example, "Zifencei" names the instruction-fetch fence extension
+last letter is "p". For example, "Zifencei" names the instruction-fetch fence extension
 described in <<zifencei>>; "Zifencei2" and "Zifencei2p0" name version 2.0 are the same.
 
 The first letter following the "Z" conventionally indicates the most
@@ -104,7 +104,7 @@ Other standard extensions that extend the supervisor-level architecture are
 named by using "Ss" as a prefix, followed by an alphanumeric name. The name 
 must end with an alphabetical character or an optional 
 version number. The second letter from the end cannot be numeric character
-if the last letter is ``p''. Supervisor-level extensions must be separated 
+if the last letter is "p". Supervisor-level extensions must be separated 
 from other multi-letter extensions by an underscore. These extensions are further 
 defined in Volume II.
 
@@ -139,7 +139,7 @@ listed, they should be ordered alphabetically.
 Non-standard extensions are named by using a single "X" followed by the alphanumeric 
 name. The name must end with an alphabetic character or an optional version number. The 
 second letter from the end cannot be numeric if the last letter is 
-``p''. For example, "Xhwacha" names the Hwacha vector-fetch ISA 
+"p". For example, "Xhwacha" names the Hwacha vector-fetch ISA 
 extension; "Xhwacha2" and "Xhwacha2p0" name version 2.0 of same.
 
 Non-standard extensions must be listed after all standard extensions, and,