Document inclusive range in help for "find"

PR gdb/16930 points out that the "find" command uses an inclusive
range; but this is not documented in the "help".  This patch updates
the help text.

gdb/ChangeLog
2020-10-07  Tom Tromey  <tromey@adacore.com>

	PR gdb/16930:
	* findcmd.c (_initialize_mem_search): Mention that the range is
	inclusive.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2020-10-07  Tom Tromey  <tromey@adacore.com>
+
+	PR gdb/16930:
+	* findcmd.c (_initialize_mem_search): Mention that the range is
+	inclusive.
+
 2020-10-07  Tom Tromey  <tromey@adacore.com>
 
 	* target.h (simple_search_memory): Don't declare.

gdb/findcmd.c

@@ -292,6 +292,7 @@ find [/SIZE-CHAR] [/MAX-COUNT] START-ADDRESS, +LENGTH, EXPR1 [, EXPR2 ...]\n\
 SIZE-CHAR is one of b,h,w,g for 8,16,32,64 bit values respectively,\n\
 and if not specified the size is taken from the type of the expression\n\
 in the current language.\n\
+The two-address form specifies an inclusive range.\n\
 Note that this means for example that in the case of C-like languages\n\
 a search for an untyped 0x42 will search for \"(int) 0x42\"\n\
 which is typically four bytes, and a search for a string \"hello\" will\n\