devel/gcvs: unbreak with libc++ 3.9

AppGlue.cpp:263:9: error: cannot initialize a variable of type 'char *' with an rvalue of type 'const char *'

char *login = strchr(ccvsroot, '@');
      ^       ~~~~~~~~~~~~~~~~~~~~~

CvsArgs.cpp:201:16: error: call to 'strchr' is ambiguous

bool hasLF = strchr(newarg, '\n') != 0L;
             ^~~~~~

CvsArgs.cpp:210:19: error: call to 'strchr' is ambiguous

bool hasSpace = strchr(newarg, ' ') != 0L;
                ^~~~~~

TextBinary.cpp:466:8: error: cannot initialize a variable of type 'char *' with an rvalue of type 'const char *'

char *tmp = strrchr(file, '.');
      ^     ~~~~~~~~~~~~~~~~~~

UCvsFiles.cpp:2020:12: error: call to 'strchr' is ambiguous

if((tmp = strchr(r1, '.')) != 0L)
          ^~~~~~

UCvsFiles.cpp:2028:12: error: call to 'strchr' is ambiguous

if((tmp = strchr(r2, '.')) != 0L)
          ^~~~~~

umenu.cpp:257:12: error: call to 'strchr' is ambiguous

if((tmp = strchr(copy, '\t')) != 0L)
          ^~~~~~

umenu.cpp:280:12: error: call to 'strchr' is ambiguous

if((tmp = strchr(title, '&')) != 0L)
          ^~~~~~

Reported by: pkg-fallout