Update INSTALL.rst to talk about botan-2, and give priority to 2 over 1.11

INSTALL.rst

@@ -41,10 +41,9 @@ udns_ (optional, but recommended)
  performances when connecting to a big number of IRC servers at the same
  time.
 
-libbotan_ 1.11 (optional)
+libbotan_ 1.11 or 2.0 (optional)
  Provides TLS support. Without it, IRC connections are all made in
  plain-text mode.
- Other branches than the 1.11 are not supported.
 
 litesql_ (optional)
  Provides a way to store various options in a (sqlite3) database. Each user

louloulibs/cmake/Modules/FindBOTAN.cmake

@@ -16,10 +16,10 @@
 # This file is in the public domain
 
 find_path(BOTAN_INCLUDE_DIRS NAMES botan/botan.h
-  PATH_SUFFIXES botan-1.11 botan-2
+  PATH_SUFFIXES botan-2 botan-1.11
   DOC "The botan include directory")
 
-find_library(BOTAN_LIBRARIES NAMES botan botan-1.11 botan-2
+find_library(BOTAN_LIBRARIES NAMES botan botan-2 botan-1.11
   DOC "The botan library")
 
 # Use some standard module to handle the QUIETLY and REQUIRED arguments, and