Fix bug in reserved name matching

The regexp for matching reserved names didn't start with '^', which
means file names with matching substrings triggered it.  A file named
"icon.gif" shouldn't trigger this because "con" is in the name.  The
fix prevents this problem.

dev/git-tools/hooks/pre-commit

@@ -38,7 +38,7 @@ git diff --cached --name-only --diff-filter=A -z $against | while IFS= read -r -
 
   # Reserved names plus possible extension
   # CON, PRN, AUX, NUL, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9
-  reservednames=$(echo -n "$filename" | LC_ALL=C grep -i -E '(CON|PRN|AUX|NUL|COM1|COM2|COM3|COM4|COM5|COM6|COM7|COM8|COM9|LPT1|LPT2|LPT3|LPT4|LPT5|LPT6|LPT7|LPT8|LPT9).[a-z]{3}' | wc -c)
+  reservednames=$(echo -n "$filename" | LC_ALL=C grep -i -E '^(CON|PRN|AUX|NUL|COM1|COM2|COM3|COM4|COM5|COM6|COM7|COM8|COM9|LPT1|LPT2|LPT3|LPT4|LPT5|LPT6|LPT7|LPT8|LPT9).[a-z]{3}' | wc -c)
 
   # No trailing period or space
   trailingperiodorspace=$(echo -n "$filename" | LC_ALL=C grep -E '(\.| )$' | wc -c)