[fs.conform.9945] Use inter-sentence spacing after an (uppercase) acronym

Author: morinmorin

source/iostreams.tex

@@ -12750,7 +12750,7 @@
 
 \rSec3[fs.conform.9945]{POSIX conformance}
 \pnum
-Some behavior is specified by reference to POSIX. How such behavior is actually implemented is unspecified.
+Some behavior is specified by reference to POSIX\@. How such behavior is actually implemented is unspecified.
 \begin{note}
 This constitutes an ``as if'' rule allowing implementations
 to call native