Use internal PCRE based implementation of regular expressions instead of std C++ regex library.

C++ regex library proven to be unusable for gcc 4.8 and earlier version, so
reimplement code using PCRE library in order to build workable version of
unit_test executable for CentOS 7, RHEL 7, Ubuntu 14 and SUSE Linux 12.

src/utils/regex.h

@@ -43,6 +43,7 @@ class SMatch {
  public:
     SMatch() : size_(0) { }
     size_t size() { return size_; }
+    std::string str() { return match; }
     int size_;
     std::string match;
 };