ada: Add mention of what LSP stands for

There are multiple possible interpretations of "LSP". For example,
"Language Server Protocol". This patch clarifies that the
occurrences of "LSP" in GNAT's source code refer to the Liskov
Substitution Principle.

gcc/ada/

	* einfo.ads: Mention full name of LSP.

Tested on x86_64-pc-linux-gnu, committed on master.

gcc/ada/einfo.ads

@@ -4778,7 +4778,8 @@ package Einfo is
 --       Defined in subprogram entities. Set on wrappers created to handle
 --       inherited class-wide pre/post conditions that call overridden
 --       primitives. It references the parent primitive that has the
---       class-wide pre/post conditions.
+--       class-wide pre/post conditions. LSP stands for Liskov Substitution
+--       Principle.
 
 ---------------------------
 -- Renaming and Aliasing --