numfmt: align format output values with GNU (#1745)

When converting to SI or IEC, produce values that align with the conventions
used by GNU numfmt.

- values > 10 are represented without a decimal place, so 10000 becomes 10K
  instead of 10.0K

- when truncating, take the ceiling of the value, so 100001 becomes 101K

- values < 10 are truncated to the highest tenth, so 1001 becomes 1.1K

closes #1726

tests/fixtures/numfmt/gnutest_iec-i_result.txt

@@ -0,0 +1,49 @@
+-1.1Ki
+-1.1Ki
+-1.0Ki
+-1.0Ki
+-1023
+0
+1
+1023
+1.0Ki
+1.1Ki
+1.1Ki
+1.2Ki
+1.5Ki
+1.6Ki
+1.9Ki
+2.0Ki
+2.0Ki
+2.0Ki
+2.0Ki
+2.1Ki
+10Ki
+10Ki
+10Ki
+100Ki
+100Ki
+100Ki
+949Ki
+950Ki
+950Ki
+951Ki
+951Ki
+952Ki
+990Ki
+991Ki
+995Ki
+995Ki
+996Ki
+996Ki
+997Ki
+999Ki
+1000Ki
+1023Ki
+1.0Mi
+1.0Mi
+1.0Mi
+1.1Mi
+1.0Gi
+1.0Gi
+1.1Gi

tests/fixtures/numfmt/gnutest_iec_input.txt

@@ -0,0 +1,49 @@
+-1025
+-1024.1
+-1024
+-1023.1
+-1023
+0
+1
+1023
+1024
+1025
+1126
+1127
+1536
+1537
+1945
+1946
+1996
+1997
+2048
+2049
+10188
+10189
+10240
+102348
+102349
+102400
+971776
+972288
+972800
+972801
+973824
+973825
+1013760
+1013761
+1018879
+1018880
+1018881
+1019904
+1019905
+1022976
+1022977
+1047552
+1047553
+1048575
+1048576
+1048577
+1073741823
+1073741824
+1073741825

tests/fixtures/numfmt/gnutest_iec_result.txt

@@ -0,0 +1,49 @@
+-1.1K
+-1.1K
+-1.0K
+-1.0K
+-1023
+0
+1
+1023
+1.0K
+1.1K
+1.1K
+1.2K
+1.5K
+1.6K
+1.9K
+2.0K
+2.0K
+2.0K
+2.0K
+2.1K
+10K
+10K
+10K
+100K
+100K
+100K
+949K
+950K
+950K
+951K
+951K
+952K
+990K
+991K
+995K
+995K
+996K
+996K
+997K
+999K
+1000K
+1023K
+1.0M
+1.0M
+1.0M
+1.1M
+1.0G
+1.0G
+1.1G

tests/fixtures/numfmt/gnutest_si_input.txt

@@ -0,0 +1,39 @@
+-1001
+-999.1
+-999
+1
+500
+999
+999.1
+1000
+1000.1
+1001
+9900
+9901
+9949
+9950
+9951
+10000
+10001
+10500
+10999
+50000
+99000
+99001
+99900
+99949
+99950
+100000
+100001
+100999
+101000
+101001
+999000
+999001
+999949
+999950
+999999
+1000000
+1000001
+999000000.1
+999000001

tests/fixtures/numfmt/gnutest_si_result.txt

@@ -0,0 +1,39 @@
+-1.1K
+-1.0K
+-999
+1
+500
+999
+1.0K
+1.0K
+1.1K
+1.1K
+9.9K
+10K
+10K
+10K
+10K
+10K
+11K
+11K
+11K
+50K
+99K
+100K
+100K
+100K
+100K
+100K
+101K
+101K
+101K
+102K
+999K
+1.0M
+1.0M
+1.0M
+1.0M
+1.0M
+1.1M
+1.0G
+1.0G