gnat_rm.texi, [...]: Fix spacing after `e.g.' and `i.e.' by adding comma or `@:'...

gnat_rm.texi, [...]: Fix spacing after `e.g.' and `i.e.' by adding comma or `@:' as appropriate.

* gnat_rm.texi, gnat_ugn.texi: Fix spacing after `e.g.' and
`i.e.' by adding comma or `@:' as appropriate.
* gnat_rm.texi (Pragma Wide_Character_Encoding): Instead of
plain characters `C', use `@samp{C}'.
* gnat_ugn.texi (File Naming Rules, About gnatkr)
(Krunching Method): Likewise.

From-SVN: r132642