Document the remove-null-characters transform.

Both as a new transformation function available, and as the default for
Text conversions when coming from MySQL. See #258, Fixes #219.

pgloader.1

@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "PGLOADER" "1" "November 2015" "ff" ""
+.TH "PGLOADER" "1" "December 2015" "ff" ""
 .
 .SH "NAME"
 \fBpgloader\fR \- PostgreSQL data loader
@@ -2139,22 +2139,22 @@ type decimal to decimal keep typemod
 Texts:
 .
 .IP "\(bu" 4
-type char to varchar keep typemod
+type char to varchar keep typemod using remove\-null\-characters
 .
 .IP "\(bu" 4
-type varchar to text
+type varchar to text using remove\-null\-characters
 .
 .IP "\(bu" 4
-type tinytext to text
+type tinytext to text using remove\-null\-characters
 .
 .IP "\(bu" 4
-type text to text
+type text to text using remove\-null\-characters
 .
 .IP "\(bu" 4
-type mediumtext to text
+type mediumtext to text using remove\-null\-characters
 .
 .IP "\(bu" 4
-type longtext to text
+type longtext to text using remove\-null\-characters
 .
 .IP "" 0
 .
@@ -2848,12 +2848,18 @@ Out: "{foo,bar}"
 Convert an empty string to a null\.
 .
 .IP "\(bu" 4
-\fIright\-trimg\fR
+\fIright\-trim\fR
 .
 .IP
 Remove whitespace at end of string\.
 .
 .IP "\(bu" 4
+\fIremove\-null\-characters\fR
+.
+.IP
+Remove \fBNUL\fR characters (\fB0x0\fR) from given strings\.
+.
+.IP "\(bu" 4
 \fIbyte\-vector\-to\-bytea\fR
 .
 .IP

pgloader.1.md

@@ -1791,12 +1791,12 @@ Numbers:
 
 Texts:
 
-  - type char       to varchar keep typemod
-  - type varchar    to text
-  - type tinytext   to text
-  - type text       to text
-  - type mediumtext to text
-  - type longtext   to text
+  - type char       to varchar keep typemod using remove-null-characters
+  - type varchar    to text using remove-null-characters
+  - type tinytext   to text using remove-null-characters
+  - type text       to text using remove-null-characters
+  - type mediumtext to text using remove-null-characters
+  - type longtext   to text using remove-null-characters
 
 Binary:
 
@@ -2230,10 +2230,14 @@ The provided transformation functions are:
 
     Convert an empty string to a null.
 
-  - *right-trimg*
+  - *right-trim*
 
     Remove whitespace at end of string.
 
+  - *remove-null-characters*
+
+    Remove `NUL` characters (`0x0`) from given strings.
+
   - *byte-vector-to-bytea*
 
     Transform a simple array of unsigned bytes to the PostgreSQL bytea Hex