fio: allow milliseconds on all time specifiers

This patch allows all time specifiers to be specified down to
milliseconds.  Default will stay seconds for compatibility with old
configs.

It also adds documentation to the existing time units day, hour and
minute.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/fio.1 b/fio.1
index aadb5ce..a16d039 100644
--- a/fio.1
+++ b/fio.1
@@ -121,12 +121,16 @@
 SI integer: a whole number, possibly containing a suffix denoting the base unit
 of the value.  Accepted suffixes are `k', 'M', 'G', 'T', and 'P', denoting
 kilo (1024), mega (1024^2), giga (1024^3), tera (1024^4), and peta (1024^5)
-respectively. The suffix is not case sensitive. If prefixed with '0x', the
-value is assumed to be base 16 (hexadecimal). A suffix may include a trailing 'b',
-for instance 'kb' is identical to 'k'. You can specify a base 10 value
-by using 'KiB', 'MiB', 'GiB', etc. This is useful for disk drives where
-values are often given in base 10 values. Specifying '30GiB' will get you
-30*1000^3 bytes.
+respectively. If prefixed with '0x', the value is assumed to be base 16
+(hexadecimal). A suffix may include a trailing 'b', for instance 'kb' is
+identical to 'k'. You can specify a base 10 value by using 'KiB', 'MiB','GiB',
+etc. This is useful for disk drives where values are often given in base 10
+values. Specifying '30GiB' will get you 30*1000^3 bytes.
+When specifying times the default suffix meaning changes, still denoting the
+base unit of the value, but accepted suffixes are 'D' (days), 'H' (hours), 'M'
+(minutes), 'S' Seconds, 'ms' milli seconds. Time values without a unit specify
+seconds.
+The suffixes are not case sensitive.
 .TP
 .I bool
 Boolean: a true or false value. `0' denotes false, `1' denotes true.