Fix static MinGW build

[rockdaboot]

Copied over the comments and macro tree from src/pcre2_internal.h, which I consider to be correctly.

Fixes #243

[carenas]

(which is included below)

this is not correct in this context

[rockdaboot]

I amended the comment.

[carenas]

This breaks the non static build as shown by:

src/pcre2posix.c:62: warning: "PCRE2POSIX_EXP_DECL" redefined
   62 | #  define PCRE2POSIX_EXP_DECL extern __declspec(dllexport)
      | 
In file included from src/pcre2posix.c:52:
src/config.h:257: note: this is the location of the previous definition
  257 | #define PCRE2POSIX_EXP_DECL extern __attribute__ ((visibility ("default")))
      | 
src/pcre2posix.c:63: warning: "PCRE2POSIX_EXP_DEFN" redefined
   63 | #  define PCRE2POSIX_EXP_DEFN __declspec(dllexport)
      | 
src/config.h:260: note: this is the location of the previous definition
  260 | #define PCRE2POSIX_EXP_DEFN extern __attribute__ ((visibility ("default")))
      | 

[rockdaboot]

This breaks the non static build as shown by:

src/pcre2posix.c:62: warning: "PCRE2POSIX_EXP_DECL" redefined
   62 | #  define PCRE2POSIX_EXP_DECL extern __declspec(dllexport)
      | 
In file included from src/pcre2posix.c:52:
src/config.h:257: note: this is the location of the previous definition
  257 | #define PCRE2POSIX_EXP_DECL extern __attribute__ ((visibility ("default")))
      | 
src/pcre2posix.c:63: warning: "PCRE2POSIX_EXP_DEFN" redefined
   63 | #  define PCRE2POSIX_EXP_DEFN __declspec(dllexport)
      | 
src/config.h:260: note: this is the location of the previous definition
  260 | #define PCRE2POSIX_EXP_DEFN extern __attribute__ ((visibility ("default")))
      | 

This happens without this PR as well (commit 04fbb65).

[rockdaboot]

Removed the (superfluous) defines from src/pcre2posix.c.

[carenas]

Those defines weren't superfluous. As explained in the documentation[1] the code you are adding is linking to, you need to set them differently depending of if you are building the library or a program that uses it.

There is an interesting takeaway from your accidental solution though, and it is that the __declspec(dllimport) is actually optional[2], and that could be exploited (albeit with a small performance hit) to avoid having to keep track of the way the library was build with PCRE2_STATIC, and which is the root cause of the problem as shown in #246.

[1] https://web.archive.org/web/20130907051123/http://msdn.microsoft.com/en-us/library/y4h7bcy6(VS.80).aspx
[2] https://learn.microsoft.com/en-us/cpp/build/importing-into-an-application-using-declspec-dllimport

[rockdaboot]

Superceded by #249