subtract 'a' from indices for marks

Given:

static int marks['z' - 'a'];
marks[c];

In this case c is the character read and index is out of bounds. We
need marks[c - 'a']

While playing around with optimization settings gcc caught caught this.

Also fix one check for c, change from isalpha to islower.

-emg

From 2cc36818283e9068576c1042690c016a81b709a3 Mon Sep 17 00:00:00 2001
From: Evan Gates <evan.gates@gmail.com>
Date: Fri, 15 Jul 2016 09:52:39 -0700
Subject: [PATCH] fix marks indexing
1 file changed
tree: 24aeabe7be7643e264bea787383c42a7aaaa4a46
  1. libutf/
  2. libutil/
  3. arg.h
  4. basename.1
  5. basename.c
  6. cal.1
  7. cal.c
  8. cat.1
  9. cat.c
  10. chgrp.1
  11. chgrp.c
  12. chmod.1
  13. chmod.c
  14. chown.1
  15. chown.c
  16. chroot.1
  17. chroot.c
  18. cksum.1
  19. cksum.c
  20. cmp.1
  21. cmp.c
  22. cols.1
  23. cols.c
  24. comm.1
  25. comm.c
  26. compat.h
  27. config.mk
  28. cp.1
  29. cp.c
  30. cron.1
  31. cron.c
  32. crypt.h
  33. cut.1
  34. cut.c
  35. date.1
  36. date.c
  37. dirname.1
  38. dirname.c
  39. du.1
  40. du.c
  41. echo.1
  42. echo.c
  43. ed.1
  44. ed.c
  45. env.1
  46. env.c
  47. expand.1
  48. expand.c
  49. expr.1
  50. expr.c
  51. false.1
  52. false.c
  53. find.1
  54. find.c
  55. flock.1
  56. flock.c
  57. fold.1
  58. fold.c
  59. fs.h
  60. getconf.1
  61. getconf.c
  62. getconf.sh
  63. grep.1
  64. grep.c
  65. head.1
  66. head.c
  67. hostname.1
  68. hostname.c
  69. join.1
  70. join.c
  71. kill.1
  72. kill.c
  73. LICENSE
  74. link.1
  75. link.c
  76. ln.1
  77. ln.c
  78. logger.1
  79. logger.c
  80. logname.1
  81. logname.c
  82. ls.1
  83. ls.c
  84. Makefile
  85. md5.h
  86. md5sum.1
  87. md5sum.c
  88. mkdir.1
  89. mkdir.c
  90. mkfifo.1
  91. mkfifo.c
  92. mktemp.1
  93. mktemp.c
  94. mv.1
  95. mv.c
  96. nice.1
  97. nice.c
  98. nl.1
  99. nl.c
  100. nohup.1
  101. nohup.c
  102. od.1
  103. od.c
  104. paste.1
  105. paste.c
  106. pathchk.1
  107. pathchk.c
  108. printenv.1
  109. printenv.c
  110. printf.1
  111. printf.c
  112. pwd.1
  113. pwd.c
  114. queue.h
  115. readlink.1
  116. readlink.c
  117. README
  118. renice.1
  119. renice.c
  120. rm.1
  121. rm.c
  122. rmdir.1
  123. rmdir.c
  124. sed.1
  125. sed.c
  126. seq.1
  127. seq.c
  128. setsid.1
  129. setsid.c
  130. sha1.h
  131. sha1sum.1
  132. sha1sum.c
  133. sha224.h
  134. sha224sum.1
  135. sha224sum.c
  136. sha256.h
  137. sha256sum.1
  138. sha256sum.c
  139. sha384.h
  140. sha384sum.1
  141. sha384sum.c
  142. sha512-224.h
  143. sha512-224sum.1
  144. sha512-224sum.c
  145. sha512-256.h
  146. sha512-256sum.1
  147. sha512-256sum.c
  148. sha512.h
  149. sha512sum.1
  150. sha512sum.c
  151. sleep.1
  152. sleep.c
  153. sort.1
  154. sort.c
  155. split.1
  156. split.c
  157. sponge.1
  158. sponge.c
  159. strings.1
  160. strings.c
  161. sync.1
  162. sync.c
  163. tail.1
  164. tail.c
  165. tar.1
  166. tar.c
  167. tee.1
  168. tee.c
  169. test.1
  170. test.c
  171. text.h
  172. tftp.1
  173. tftp.c
  174. time.1
  175. time.c
  176. TODO
  177. touch.1
  178. touch.c
  179. tr.1
  180. tr.c
  181. true.1
  182. true.c
  183. tsort.1
  184. tsort.c
  185. tty.1
  186. tty.c
  187. uname.1
  188. uname.c
  189. unexpand.1
  190. unexpand.c
  191. uniq.1
  192. uniq.c
  193. unlink.1
  194. unlink.c
  195. utf.h
  196. util.h
  197. uudecode.1
  198. uudecode.c
  199. uuencode.1
  200. uuencode.c
  201. wc.1
  202. wc.c
  203. which.1
  204. which.c
  205. whoami.1
  206. whoami.c
  207. xargs.1
  208. xargs.c
  209. xinstall.1
  210. xinstall.c
  211. yes.1
  212. yes.c