[devel] Relocated a single quote from the beginning of a line in the manual

It interfered with nroff processing.
diff --git a/libpng-manual.txt b/libpng-manual.txt
index 3fa5374..80240ec 100644
--- a/libpng-manual.txt
+++ b/libpng-manual.txt
@@ -198,9 +198,9 @@
 rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
 
 Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing
-the lines defining the supported features, paying very close attention to the
-'option' information in scripts/pnglibconf.dfa that describes those features and
-their requirements.  This is easy to get wrong.
+the lines defining the supported features, paying very close attention to
+the 'option' information in scripts/pnglibconf.dfa that describes those
+features and their requirements.  This is easy to get wrong.
 
 B. Configuration using DFA_XTRA
 
diff --git a/libpng.3 b/libpng.3
index e2c6747..7762270 100644
--- a/libpng.3
+++ b/libpng.3
@@ -1153,9 +1153,9 @@
 rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
 
 Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing
-the lines defining the supported features, paying very close attention to the
-'option' information in scripts/pnglibconf.dfa that describes those features and
-their requirements.  This is easy to get wrong.
+the lines defining the supported features, paying very close attention to
+the 'option' information in scripts/pnglibconf.dfa that describes those
+features and their requirements.  This is easy to get wrong.
 
 B. Configuration using DFA_XTRA