filesets: ignore unit case in size() predicate for single value

When specifying one plain value in size(), e.g. size(1k), fileset tries to
guess the upper bound automatically (see the comment in _sizetomax()). It
didn't ignore the specified unit's case, and so size("1 GB"), for example,
produced this error:

hg: parse error: couldn't parse size: 1 GB

Let's do the same thing that util.sizetoint() does: .lower().

The two test lines without output just check that there are no parse errors.

mercurial/fileset.py

@@ -287,7 +287,7 def grep(mctx, x):
 
 def _sizetomax(s):
     try:
-        s = s.strip()
+        s = s.strip().lower()
         for k, v in util._sizeunits:
             if s.endswith(k):
                 # max(4k) = 5k - 1, max(4.5k) = 4.6k - 1

tests/test-fileset.t

@@ -144,6 +144,8 Test files properties
   2k
   $ fileset '(1k or 2k) and size(".5KB - 1.5kB")'
   1k
+  $ fileset 'size("1M")'
+  $ fileset 'size("1 GB")'
 
 Test merge states